tal modem calls. Q. Does this feature require new hardware in the 3600? A. No Q. What network modules support this feature? A. All the current 1/2 PRI NMs, including the new 1FE 1/2 PRI NM. Q.Is the Cisco Dial-out Utility supported through an R2 connection? A. Yes. Version 2 of the Cisco Dial-out Utility (available early November) together with MICA Portware 2.5.1.0 support Dial/Fax out through the R2 interface Q. Is this R2 feature supported the Cisco 2600, 3620, and 3640? A. The ability for Modem calls to be terminated through an R2 interface is available for all platforms that support Cisco digital modems. This currently limits R2 support to the 3640/3620 Q. Do I need a new version of the digital modem microcode to support R2? A. No. All shipping versions of Portware are supported. For information on Portware and instructions on downloading the latest version, please visit: http://www.cisco.com/public/sw-center/sw-access.shtml. Q. What IOS is required to utilize this feature? A. IOS 12.0(1)T and above Q. Can I support ISDN PRI R2, and CAS in the same chassis? A. Yes, on a per network module basis. Each individual PRI NM can be configured as R2,CAS or ISDN PRI. Q. What countries will this R2 feature be available in? A. At FCS, a subset of the 5300 supported R2 countries will be supported. All Countries in the list above have been successfully tested internally. Q. Will the new mixed media FE/PRI support R2? A. Yes. Q. Can two PRI/R2 links share one DM NM? A. Yes. The pool of modems is available to all R2/PRI interfaces. 99.6>Q: Kogda zhe nakonec budet reliz V.90 dlya MICA ? >A: (Oleg Zharoff) Vyshel nakonec dolgozhdannyj reliz V.90 dlya MICA modemov, versiya 2.5.1.0. http://www.cisco.com/univercd/cc/td/doc/product/access/acs_serv/5300/ mod_info/53fw_pw/53micaa/rn250x.htm 99.7>Q: A vot pochemu ya ne mogu cherez console zajti na moyu ciscu? I nastrojki krutil, i porty na mashinkah zhivye, a chto ne tak - ne pojmu. >A: Pavel Stepchenko McFlySr@irc Prover'te marku vashej motherboard. Esli eto Atrend, prover'te, "rodnye" li "kosichki"? Delo v tom, chto poganye(kto mne vozmestit dushevnoe ravnovesie?! ;) ) kitajcy reshili, chto oni umnee vseh, i zayuzali "kosichki" s shahmatnoj raspajkoj(kak i na AT486); na ostal'nyh zhe MB - pryamaya raspajka. Esli ne ATREND - vse ravno prover'te porty na celostnost', tak kak cu po umolchaniyu imeet Xon/Xoff i voobshche :) Ubezhdaemsya, chto na cuaa0(1) ne visit (m)getty, puskaem cu -l /dev/cuaa0(1), i naslazhdaemsya zhizn'yu :) Thanks for support: CGHost, Fifo, Jimson, Lee7, Mdh, ReedCat, vul. 99.8>Q: Tut problema - kto znaet kak vystavit' nomer seti u Hovell'nogo klienta ? Hachal bit' setku na VLANy - i voznikli problemy. MS rabotaet normal'no, a Hovel'nyj klient ne hochet. >A: (Serge Turchin) Propisat' spantree portfast na portah Katalista. [13.06.2000] 99.8.1>Q: Kak zastavit' porty na 2924XL bystree inicializirovat'sya ? >A: os@alkar.net http://www.cisco.com/warp/public/473/12.html 99.9>Q: Kto-nibud' znaet, kak byt' s uteryannym parolem na 1020? >A: (Gleb Pijov) Question: How do you recover lost passwords on a Cisco 1020? Answer: As the Cisco 1020 is rarely physically secured, password recovery is done by calling Cisco and providing a system generated CHALLENGE. Using the override program, the support engineer can provide a one-time password to use to get into enable mode. Then, follow these steps: 1.Customer: Put up dip switch 1 and apply power. You should see "Console Username:". 2.Customer : Login with Username "enable" and Password "override". It will print a CHALLENGE. 3.Cisco runs the override program and prints a RESPONSE. 4.Customer: On the 1020, log in as "enable" and give the RESPONSE as the password. That will get you the # prompt, then you can do a wr t to see the current enable password. Or, you can do a config t and reset the enable password. 99.10>Q: Problemy s MTU na interface tunnel. >A: "Philipp V. Patrushoff" BugID: CSCdm54169 >>> [13.09.2000] Vladislav Nebolsine, NB !!! >>> bag ispravlen v 11.3(11) i 12.0(6) You cannot change the MTU size of a tunnel interface using software after Cisco IOS Release +11.3(9.2). Workarounds: Use images between Release 11.3(5.1)T and Release 11.3(9.3) or Release 12.0(0.16) and Release 12.0(4.2). Configure ip mtu on the tunnel interface before you configure tunnel destination. If tunnel destination is already configured, then unconfigure the destination, configure ip mtu, and then reconfigure the destination. You need to wait five seconds after removing the tunnel destination before issuing the ip mtu command. Once the workaround is issued, there should be no problems in the event of a router reboot as the ip mtu command is parsed before the tunnel destination. [27.12.2000] 99.11>Q:Est' neskol'ko Kisok sepii 25xx. Hyzhno odnovpemenno na vseh v oppedelennyj moment menyat' X25 routing, ppichem zhelatel'no odnim skpiptom iz-pod FreeBSD. Kak ? >A: A: (Alex Bakhtin), (John Gladkih), (Vladislav Staroselsky) === newconfig === interface serial shutdown exit no x25 route ... x25 route ... interface serial no shutdown end === newconfig === === Cisco config === ip rcmd rcp-enable ip rcmd remote-host enable ip rcmd remote-username rlogin trusted-remoteuser-source local rlogin trusted-localuser-source local === Cisco config === === change_routing.sh === #!/bin/sh su -c "rcp newconfig @:running-config" === change_routing.sh === V newconfig vstavlyaem nyzhnye izmeneniya tekyshchego poytinga (chepez no route i route). Ppopisyvaem na FreeBSD yuzepa. V nyzhnyj moment zapyskaem change_routing.sh ===========================================================

NN. Zametki na polyah.

=========================================================== Sergey Trofimovsky - PPP per-user timeouts explained http://www.employees.org/~dpeng/per_user_timeout.htm Kstati govorya, nachinaya s 11.3(8)T (ili AA :-) timeouts uzhe i v PPP/PAP rabotayut.Bez izvratov v vprofiles etc. Dmitriy Yermakov - gde-to nachinaya s 11.3(5)T poyavilos' ppp authorization per interface teper' mozhno otklyuchat' avtorizaciyu na leased line s enc ppp Serge Turchin - V 12.03T poyavilsya X.25 over FR... Vladislav Nebolsine - Hu, a podrobnee ob etoj opcii mozhno prochitat' zdes' http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120t/120t3/x25anxg.htm Dmitriy Yermakov - trebovaniya k ob®emu pamyati http://infoblast.comptek.ru/cpqrg/cpqrg2.htm#xtocid2097032 Cisco-on-line Conference on Comptek http://online.comptek.ru/cisco/index.html Martin McFlySr Cisco Year 2000 Product Compliance URL http://www.cisco.com/warp/public/cc/cisco/mkt/gen/2000/prodlit/cptbl_ov.htm Dmitriy Yermakov - Problemy s Zelax M115 na svyazke cisco-unix, reshenie ot Igorya Nikolaeva - http://knot.pu.ru/faq/pppd.html Raspajki razlichnyh kabelej, konfigi dlya modemov - http://www.links.ru [13.06.2000] Cisco IOS Software RoadMap - http://www.cisco.com/warp/public/620/roadmap.shtml [13.06.2000] Vasily Ivanov - Ogranichenie skorosti konnekta dlya MICA modemov - http://www.cisco.com/univercd/cc/td/doc/product/access/acs_serv/5300/mod_info/at/atcmnds.htm [04.07.2000] Vladislav Nebolsine - Esli komu interesno - v 12.1(2)XH poyavilas' - podderzhka E1 R2 dlya 2600/3600/7200, - Caller ID dlya 3810/2600/3600, - ISDN PRI Q.931 User-Side/Network-Side dlya golosovyh modulej 2600/3600 (do etogo byl tol'ko Q.SIG) - i koe-chto drugoe. Podrobnosti: http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121limit/121x/121xh/121xh_2/index.htm [04.07.2000] Poltergejst v NM-*AM (Problemy s NM-8AM (NM-16AM)) Simptomy: 1. Modemy ne berut trubu pri vhodyashchem zvonke. 2. Modemy pokazyvayut nalichie vhodyashchego zvonka prosto pri podklyuchenii k tel.linii. 3. Pri zvonke obratnym telnetom na obychnyj telefon - vmesto handshack-signala - rev 50 gc. Zazemlite cisku. [27.12.2000] Yuri Vorobyev - Cisco ground http://www.cisco.com/univercd/cc/td/doc/product/access/acs_mod/cis3600/3600_ cn/nebslugs.htm [02.08.2000] Gosha Zafievsky NM-8AM, NM-16AM _ne_ podderzhivayut rezhim leased line. P.S. (DY) ZHelayushchie mogut poeksperimentirovat' s ATA i bol'shIm vremenem ozhidaniya CARRIER. Za rezul'tat ne ruchayus'. [12.09.2000] john gladkih - LL na MCOM modemah (NM-8/16AM) kogo interesovali LL na MCOM modemah? ono rabotaet. my zavodili 18 vol't na korotkoj linii. cherez DDR+RIP [05.09.2000] Victor L. Belov - Tunnel' s win98 na cisco router variantov 2 =-) 1. pptp podderzhivaetsya tol'ko v special'nom IOS (12.0.7XE chto li... ne pomnyu tochno) na 7xxx marshrutizatorah. S drugoj storony pptpd na FreeBSD i Linux rabotaet normal'no. 2. na melkih marshrutizatorah podderzhivaetsya l2tp tunneli, no togda na 95/98/NT pridetsya stavit' dop. klient - naprimer WinVPN ot http://www.routerware.com V Windows 2000 est' vstroennaya podderzhka l2tp. YA dazhe zavel mezhdu nim i Cisco IPSec - poluchaetsya sovsem horosho. [22.10.2000] (DY) psevdovydelenka na chem ugodno, kak podnimat' kanal. Kak nastraivat' DDR - chitat' doki. A chtoby kiska sama podnimala kanal ne zavisimo ot aktivnosti v seti, navernoe, imeet smysl nastroit' ntp na kiske :) [24.10.2000] Basil Dolmatov - 17xx ne podderzhivaet ISL, hardware limitation. I ne budet podderzhivat'. [09.12.2000] Valery Filippov - 4500 ne tyanet 4Mbit na DCE. [27.12.2000] Eugeny Krasilnikov - undocumented Cisco IOS commands http://boerland.com/dotu http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t1/sshv1.htm#10313 * Cisco-networking-FAQ * Subject: comp.dcom.sys.cisco Frequently Asked Questions (FAQ) Date: 12 Sep 1997 From: jhawk@panix.com (John Hawkinson) Organization: PANIX Public Access Internet and Unix, NYC Newsgroups: comp.dcom.sys.cisco, comp.protocols.tcp-ip, comp.dcom.servers, comp.answers, news.answers Archive-name: cisco-networking-faq Last-modified: $Date: 1996/04/28 05:55:19 $ Version: $Revision: 1.10 $ This FAQ is edited by John Hawkinson, . Administrivia: Please contribute answers to the questions in the Todo section! If your answer is somewhat complicated, posting would probably be best (to comp.dcom.sys.cisco). Otherwise, e-mail it to cisco-faq@panix.com. Please note that a LOT of these questions have been hanging around for some time, and if knowledgable people could take the time to answer a few of them, that'd help. This draft FAQ is in RFC1153 digest format, so you can follow each question with your newsreader. I suppose that question-numbers should be moved to the From: field. Note that Date: fields represent last-modification times for the questions. Since this FAQ was first developed, cisco has written up a lot of useful information on their web site, http://www.cisco.com. If you can't find what you're looking for here, please check there, too. Table of Contents ================= 1. How can I contact cisco? 2. What is this newsgroup? 3. What does ``cisco'' stand for? 4. How do I save the configuration of a cisco? 5. Where can I get ancillary software for my cisco? 6. Is there a World-Wide-Web (www) information source? 7. How can I get my cisco to talk to a third party router over 8. How can I get my cisco to talk to a 3rd-party router over Frame Relay? 9. How can I use debugging? 10. How can I use NTP (Network Time Protocol) with my cisco? 11. Sample cisco NTP Configurations 12. How do I avoid the annoying DNS lookup if I have misspelled a command? 13. Tracing bad routing information 14. How to use access lists 15. The cisco boot process 16. Where can I get cisco hardware? 17. Where can I get IETF documents (RFCs, STDs, etc.)? 18. Future features in cisco software 19. How do cisco routers rate performance-wise? 20. How are packets switched? 21. How does one interpret buffer statistics? 22. How should I restrict access to my router? 23. What can I do about source routing? 24. Is there a block of private IP addresses I can use? 25. Is DHCP supported? 26. Where can I get cisco documentation? 27. What's the latest software for the CSC/3? 28. What IP routing protocol should I use? 29. How do I interpret the output of ``show version''? 30. What is the maximum number of Frame Relay PVCs? 31. How much memory is necessary to telnet to a cisco router? 32. Where can I purchase flash RAM? 33. When are static routes redistributed? 34. When is the next hop of a route considered ``reachable''? 35. How do name and phone number of ``dialer map'' interfere? 36. What's the purpose of the network command? 37. What is VLSM? 38. What are some methods for conserving IP addresses for serial lines? 39. Why do some ip addresses get rejected? 40. How do 4xxx serial numbers correspond to models? 41. Where can I find more info on TACACS+ 99. Acknowledgements. todo: ===== * What is SNMP and how can I use it? What software is available and how do I use cisco enterprise MIBs? MIBs on ftpeng.cisco.com and CIO.cisco.com * Pointers to other net resources, like comp.protocols.tcp-ip, RFCs, the firewalls mailing list, etc (bgpd?[or is it cidrd now? :-)]). * Hints about confusing and not-well documented things like xtacacs... * Comments on interoperability issues WRT other vendors. * What's SMARTnet, why should I subscribe, how much does it cost, and what do I get? * What should I name my router, my interfaces, etc.? * Should we adjust the buffer parameters on the routers? What should be the indicator before tunning the buffer parameters? How should one fine tune the buffer parapeters? * What is CIDR and why do I care (or a more general acronym decoder) ? * How do I configure my cisco to use variable-length subnetting ? * Is there a block of private network numbers I can use within my organization only? When should I use them? How do I access them from outside? * What do I do if I have to partition a network number? * Questions and answers about access lists access-list reference list (lots of questions on that) * I forgot to mention that routing DECnet over X.25 is a problem. * Where PD network applications for SLIP/PPP are. * What is HSRP and how does it work? When is it available (10.0) (Hot Standby Routing Protocol) * Should I run 10.0, 10.2, 10.3, 11.1, or what? * What's the difference between IBGP and EBGP? Why should I run BGP? Actual content. =============== ------------------------------ How can I contact cisco? From: Question 1 Date: 31 October 1994 Corporate address: cisco Systems 170 West Tasman Drive San Jose, CA 95134 The following phone numbers are available: Technical Assistance Center (TAC) +1 800 553 2447 (553 24HR) +1 800 553 6387 +1 408 526 8209 Customer Service (Documentation, Warranty & +1 800 553 6387 Contract Services, Order Status Engineering +1 800 553 2447 (553 24HR) On-site Services, Time & Materials Service +1 800 829 2447 (829 24HR) Corporate number / general +1 408 526 4000 Corporate FAX (NOT tech support) +1 408 526 4100 The above 800 numbers are US/Canada only. cisco can also be contacted via e-mail: tac@cisco.com Technical Assistance Center tac-euro@cisco.com European TAC cs-rep@cisco.com Literature and administrative (?) requests cs@cisco.com *UNRELIABLE*, special-interest, ``non-support'' Please follow the directions available on CIO before doing this. cisco provides an on-line service for information about their routers and other products, called CIO (cisco Information Online). telnet to cio.cisco.com for more details. The collective experience of this FAQ indicates that it is far wiser to open a case using e-mail than FAXes, which may be mislaid, shredded, etc. For those of you still in the paperfull office (unlike the rest of us), cisco Systems' new corporate address is: 170 West Tasman Drive San Jose, CA 95134 Mail to tac@cisco.com should include your service contract number, your name, telephone number, a brief one line problem/question description, and a case priority in the first 5 lines. For example: Cisco service contract number 92snt1234a First and last name Jane Doe Best number to contact you 415-555-1234 Problem/question description Cannot see Appletalk zones Case Priority 3 CASE PRIORITIES are defined as one of the following: Pri 1 Production network down, critical business impact Pri 2 Production net seriously degraded, serious impact Pri 3 Network degraded, noticeable impact to business Pri 4 General information, non production problems ------------------------------ What is this newsgroup? From: Question 2 Date: 26 July 1994 comp.dcom.sys.cisco, which is gatewayed to the mailing list cisco@spot.colorado.edu, is a newsgroup for discussion of cisco hardware, software, and related issues. Remember that you can also consult with cisco technical support. This newsgroup is not an official cisco support channel, and should not be relied upon for answers, particularly answers from cisco Systems employees. Until recently, the mailing list was gatewayed into the newsgroup, one-way. It is possible that this arrangement may resume at somet time in the future. ------------------------------ What does ``cisco'' stand for? From: Question 3 Date: 31 October 1994 cisco folklore time: At one point in time, the first letter in cisco Systems was a lowercase ``c''. At present, various factions within the company have adopted a capital ``C'', while fierce traditionalists (as well as some others) continue to use the lowercase variant, as does the cisco Systems logo. This FAQ has chosen to use the lowercase variant throughout. cisco is not C.I.S.C.O. but is short for San Francisco, so the story goes. Back in the early days when the founders Len Bosack and Sandy Lerner and appropriate legal entities were trying to come up with a name they did many searches for non similar names, and always came up with a name which was denied. Eventually someone suggested ``cisco'' and the name wasn't taken (although SYSCO may be confusingly similar sounding). There was an East Coast company which later was using the ``CISCO'' name (I think they sold in the IBM marketplace) they ended up having to not use the CISCO abberviation. Today many people spell cisco with a capital ``C'', citing problems in getting the lowercase ``c'' right in publications, etc. This lead to at least one amusing article headlined ``Cisco grows up''. This winter we will celebrate our 10th year. [This text was written in July of 1994 -jhawk] ------------------------------ How do I save the configuration of a cisco? From: Question 4 Date: 31 October 1994 If you have a tftp server available, you can create a file on the server for your router to write to, and then use the write network command. From a typical unix system: mytftpserver$ touch /var/spool/tftpboot/myconfig mytftpserver$ chmod a+w /var/spool/tftpboot/myconfig myrouter#write net Remote host [10.7.0.63]? 10.7.0.2 Name of configuration file to write [myrouter-confg]? myconfig Write file foobar on host 10.7.0.2? [confirm] y Additionally, there's a Macintosh TFTP server available: ftp://nic.switch.ch/software/mac/peterlewis/tftpd-100.sit.hqx Additionally, you can also use expect, available from: ftp://ftp.uu.net/languages/tcl/expect/expect.tar.gz ftp://ftp.cme.nist.gov/expect/expect.tar.gz or, in shar form from ftpeng.cisco.com. Expect allows you to write a script which telnets to the router and performs a ``write terminal'' command, or any other arbitrary set of command(s), using a structured scripting language (Tcl). ------------------------------ Where can I get ancillary software for my cisco? From: Question 5 Date: 5 July 1994 Try ftping to ftp://ftpeng.cisco.com/pub It's a hodgepodge collection of useful stuff, some maintained and some not. Some is also available from ftp://cio.cisco.com Vikas Aggarwal has a very customised tacacsd: A new version of xtacacsd is available via anonymous FTP from: ftp://ftp.navya.com/pub/vikas/xtacacsd-3.5.shar.gz ------------------------------ Is there a World-Wide-Web (www) information source? From: Question 6 Date: 28 April 1996 You can try the WWW page for this FAQ: http://www.panix.com/cisco-faq/ or the cisco Educational Archive (CEA) home page: http://sunsite.unc.edu/cisco/cisco-home.html or the cisco Information Online (CIO) home page: http://www.cisco.com/ ------------------------------ How can I get my cisco to talk to a third party router over a serial link? From: Question 7 Date: 5 July 1994 You need to tell your cisco to use the same link-level protocol as the other router; by default, ciscos use a rather bare variant of HDLC (High-level Data Link Control) all link-level protocols use at some level/layer or another. To make your cisco operate with most other routers, you need to change the encapsulation from HDLC to PPP on the relevant interfaces. For instance: sewer-cgs#conf t Enter configuration commands, one per line. Edit with DELETE, CTRL/W, and CTRL/U; end with CTRL/Z interface serial 1 encapsulation ppp ^Z sewer-cgs#sh int s 1 Serial 1 is administratively down, line protocol is down Hardware is MCI Serial MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec) ^^^^^^^^^^^^^^^^^^^^^^^^^^^ [...] If you're still having trouble, you might wish to turn on serial interface debugging: sewer-cgs#ter mon sewer-cgs#debug serial-interface ------------------------------ How can I get my cisco to talk to a 3rd-party router over Frame Relay? From: Question 8 Date: 27 July 1994 You should tell your cisco to use ``encapsulation frame-relay ietf'' (instead of ``encapsulation frame-relay'') on your serial interface that's running frame relay if your frame relay network contains a diverse set of manufacturers' routers. The keyword ``ietf'' specifies that your cisco will use RFC1294-compliant encapsulation, rather than the default, RFC1490-compliant encapsulation (other products, notably Novell MPR 2.11, use a practice sanctioned by 1294 but deemed verbotten by 1490, namely padding of the nlpid). If only a few routers in your frame relay cloud require this, then you can use the default encapsulation on everything and specify the exceptions with the frame-relay map command: frame-relay map ip 10.1.2.3 56 broadcast ietf ^^^^ (ietf stands for Internet Engineering Task Force, the body which evaluates Standards-track RFCs; this keyword is a misnomer as both RFC1294 and RFC1490 are ietf-approved, however 1490 is most recent and is a Draft Standard (DS), whereas 1294 is a Proposed Standard (one step beneath a DS), and is effectively obsolete). ------------------------------ How can I use debugging? From: Question 9 Date: 26 July 1994 The ``terminal monitor'' command directs your cisco to send debugging output to the current session. It's necessary to turn this on each time you telnet to your router to view debugging information. After that, you must specify the specific types of debugging you wish to turn on; please note that these stay on or off until changed, or until the router reboots, so remember to turn them off when you're done. Debugging messages are also logged to a host if you have trap logging enabled on your cisco. You can check this like so: sl-panix-1>sh logging Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns) Console logging: level debugging, 66 messages logged Monitor logging: level debugging, 0 messages logged Trap logging: level debugging, 69 message lines logged Logging to 198.7.0.2, 69 message lines logged sl-panix-1> If you have syslog going to a host somewhere and you then set about a nice long debug session from a term your box is doing double work and sending every debug message to your syslog server. Additionally, if you turn on something that provides copious debugging output, be careful that you don't overflow your disk (``debug ip-rip'' is notorious for this). One solution to this is to only log severity ``info'' and higher: sl-panix-1#conf t Enter configuration commands, one per line. End with CNTL/Z. logging trap info The other solution is to just be careful and remember to turn off debugging. This is easy enough with: sl-panix-1#undebug all If you have a heavily loaded box, you should be aware that debugging can load your router. The console has a higher priority than a vty so don't debug from the console; instead, disable console logging: cix-west.cix.net#conf t Enter configuration commands, one per line. End with CNTL/Z. no logging console Then always debug from a vty. If the box is busy and you are a little too vigorous with debugging and the box is starting to sink, quickly run, don't walk to your console and kill the session on the vty. If you are on the console your debugging has top prioority and then the only way out is the power switch. This of course makes remote debugging a real sweaty palms adventure especially on a crowded box. Caveat debugger! Also, if you for some reason forget what the available debug commands are and don't have a manual handy, remember that's what on-line help is for. Under pre 9.21 versions, ``debug ?'' lists all commands. Under 9.21 and above, that gives you general categories, and you can check for more specific options by specifying the category: ``debug ip ?''. As a warning, the ``logging buffered'' feature causes all debug streams to be redirected to an in-memory buffer, so be careful using that. Lastly, if you're not sure what debugging criteria you need, you can try ``debug all''. BE CAREFUL! It is way useful, but only in a very controlled environment, where you can turn off absolutely everything you're not interested in. Saves a lot of thinking. Turning it on on a busy box can quickly cause meltdown. ------------------------------ How can I use NTP (Network Time Protocol) with my cisco? From: Question 10 Date: 5 July 1994 >What level of software is required for NTP support in >a cisco router? 9.21 or above. >Which cisco routers support NTP? It is a software feature exclusively. Anything that supports 9.21 or 10 will run NTP (when running that s/w). >How do I set it up? The basic hook is: ntp server [version n] or ntp peer [version n] depending on whether you want a client/server or peer relationship. There's a bunch of other stuff available for MD5 authentication, broadcast, access control, etc. You can also use the context-sensitive help feature to puzzle it out; try ``ntp ?'' in config mode. You'll also want to play with the SHOW NTP * router commands. Here are two examples. EXAMPLE 1: router# show ntp assoc address ref clock st when poll reach delay offset disp +~128.9.2.129 .WWVB. 1 109 512 377 97.8 -2.69 26.7 *~132.249.16.1 .GOES. 1 309 512 357 55.4 -1.34 27.5 * master (synced), # master (unsynced), + selected, - candidate, ~ configured EXAMPLE 2: router#show ntp stat Clock is synchronized, stratum 2, reference is 132.249.16.1 nominal freq is 250.0000 Hz, actual freq is 249.9981 Hz, precision is 2**19 reference time is B1A8852D.B69201EE (12:36:13.713 PDT Tue Jun 14 1994) clock offset is -1.34 msec, root delay is 55.40 msec root dispersion is 41.29 msec, peer dispersion is 28.96 msec For particular cisco NTP questions, feel free to ask in comp.dcom.sys.cisco. For broader NTP info, see ftp://louie.udel.edu:pub/ntp/doc. The file clock.txt in that directory has info about various public NTP servers. There is also information on radio time receivers that can be connected to an NTP server (this is handy on private networks, if you have an entire campus to get chiming, or if you become a hard core chimer). The ``ntp clock-period'' command is added automagically to jump-start the NTP frequency compensation when the box is rebooted. This is essentially a representation of the frequency of the crystal used as the local timebase, and may take several days to calculate otherwise. (Do a ``write mem'' after a week or so to save a good value.) Caveat of obsolecence: Note that the CS-500 will not be able to achieve quite the same level of accuracy as other platforms, since its hardware clock resolution is roughly 242Hz instead of the 1MHz available on other platforms. In practice this shouldn't matter for anyone other than true time geeks. ---------------------------------------------------------------------- Sample cisco NTP Configurations From: Question 11 Date: 5 July 1994 You will need to substitute your own NTP peers, timezones, and GMT offsets into the examples below, of course. Example 1 is in US Central Time Zone, while example 3 is in US Pacific Time Zone. Both account for normal US Daylight Savings Time practices. EXAMPLE 1 (Charley Kline): ... clock timezone CST -6 clock summer-time CDT recurring ntp source eth 0 ntp peer ntp peer ntp peer ... EXAMPLE 2 (Tony Li): ... ntp source Ethernet0/0 ntp update-calendar ntp peer ntp peer prefer ... EXAMPLE 3 (Dave Katz): ... service timestamps debug datetime localtime service timestamps log datetime localtime clock timezone PST -8 clock summer-time PDT recurring interface Ethernet0 ip address ntp broadcast ntp clock-period 17180319 ntp source Ethernet0 ntp server ntp server ntp server COMMENTS ON EXAMPLE 3: The config file is commented with date and time (and user id, if TACACS is enabled) when the system thinks the clock is accurate. I've enabled timestamping of debug and syslog messages. I send NTP broadcast packets out onto the local ethernet. I'm in Pacific Standard Time, with U.S. standard daylight saving time rules. I use the IP address of the ethernet as the source for all NTP packets. ------------------------------ How do I avoid the annoying DNS lookup if I have misspelled a command? From: Question 12 Date: 5 July 1994 By default, all lines are configured to automatically try a telnet connection if the first word in a input line is not recognized as a valid command. You can disable this by setting ``transport preferred none'' on every line (con, aux and vty). For instance: sl-panix-1#conf t Enter configuration commands, one per line. End with CNTL/Z. line vty 0 10 transport preferred none You can see the number of vty's currently configuered with ``show lines'' Also, you can suspend connect attempts with ^^ followed by ``x'', ie shift-cntrl-6 x. [It has been suggested that ``no ip ipname-lookup'' to turn off IEN116 helps. I think this is the default -jhawk ] ------------------------------ Tracing bad routing information From: Question 13 Date: 31 Oct 1994 or: How do I find out which non-cisco systems on my networks generate IP-RIP information without letting them mess up my routing tables. Here you could work with a default administrative distance. Administrative distance is the basis upon which the cisco prefers routing information of one protocol over another. In this example: router rip network 192.125.254.0 distance 255 distance 120 192.125.254.17 ! list all valid RIP suppliers [...] the value 255 has the implicit meaning of not putting this information into the routing table. Therefore, setting an administrative distance of 255 means that all RIP suppliers are by default accepted but their information is not put into the routing table. The administrative distance for the router 192.125.244.17 has been reset to the default (for RIP) of 120, causing its routes to be accepted into the routing table. Then you can look them up with ``show ip protocols'' and restore the original administrative distance for the ones you want to fill in the routing table. The same results can be acheived with an ip access-list, but with that, ``show ip protocols'' will only show the valid ones. But often it is more useful to see which systems were generating routing information at all. This trick works for other routing protocols as well, but please select the proper adminstrative distance (rather than 120) for the protocol you're using. ------------------------------ How to use access lists From: Question 14 Date: 5 July 1994 [The following is wholesale included; at some point it'll probably be editted a bit and reformatted... -jhawk ] Frequently Asked Questions contributed by Howard C. Berkowitz PSC International hcb@world.std.com @clark.net [probably will be my permanent personal account] PSC's domain is in mid-setup Where in the router are access lists applied? In general, Basic access lists are executed as filters on outgoing interfaces. Newer releases of the cisco code, such as 9.21 and 10, do have increased ability to filter on incoming ports. Certain special cases, such as broadcasts and bridged traffic, can be filtered on incoming interfaces in earlier releases. There are also special cases involving console access. Rules, written as ACCESS-LIST statements, are global for the entire cisco box; they are activated on individual outgoing interfaces by ACCESS-GROUP subcommands of the INTERFACE major command. Filters are applied after traffic has entered on an incoming interface and gone through a routing process; traffic that originates in a router (e.g., telnets from the console port) is not subject to filtering. +-------------------+ | GLOBAL | | | | Routing | | ^ v Access | | ^ v Lists | +-^--v--------^---v-+ | ^ v ^ v | | ^ v ^ v | A----------->|-| |>>>>Access >>----------->B |1 Group 2 | <------------| |<----------- | | | | +-------------------+ Some types of ``filter,'' using ``filter'' as a broader class than ACCESS-LIST, can operate on incoming traffic. For example, the INPUT- SAP-FILTER used for Novell networks is applied to Service Advertisement Packets (SAP) seen at incoming interfaces. In general, incoming filtering can only be done for ``system'' rather than user traffic. Rules of thumb in defining access lists. First, define what you want to do and in which directions. An informal drawing is a good first step. As opposed to the usual connectivity drawings among routers, it's often convenient to draw unidirectional links between routers. Second, informally write out your filtering rules. In general, it is best to go from most specific to least specific. Modify the order of writing things to minimize the number of rules needed. Third, determine which rules need to be on which routers. Explicitly consider the direction of flow, and the possible existence of additional paths that could inadvertently bypass a filter. Can a cisco router be a ``true'' firewall? This depends on the definition of firewall. Some writers (e.g., Gene Spafford in _Practical UNIX Security_) define a firewall as a host on which an ``inside'' and/or an ``outside'' application process run, with application-level code linking the two. For example, a firewall might provide FTP access to the outside world, but it would not also provide direct FTP service to the inside world. To place a file on the FTP external server, a designated user would explicitly log onto the FTP server, transfer a file to the server, and log off. The firewall prevents direct FTP connectivity between the inside and outside networks; only indirect, application-level connectivity is allowed. Firewalls of this sort are complemented by chokes, which filter on network addresses and/or port numbers. Cisco routers cannot do application-level control with access control lists. Other authors do not distinguish between chokes and filters. Using the loose definition that a firewall is anything that selectively blocks access from the inside to the outside, routers can be firewalls. IP Specific ----------- Can the ``operand'' field be used with a protocol keyword of IP to filter on protocol ID? No. Operand filtering only works for TCP and UDP port numbers. How can I prevent traffic for a certain Internet application to flow in one direction but not the other? Remember that Internet applications flow from client port to server port. Denying traffic from port 23, for example, blocks flow from the client to the server. +-------------------+ | | A----------->| |----------->B |1 2| <------------| |<----------- | | +-------------------+ If we deny traffic to Port 23 of address B by placing a filter at interface 2, we have blocked A's ability to telnet to B, but not B's ability to telnet to A. A second filter at interface A would be needed to block telnet in both directions. Assume that we only have the filter at interface 2. Telnets to A from B will not be affected because the filter at 2 does not check incoming traffic. ------- With the arrival of in-bound access lists in 9.21, it should be noted that both inbound and access lists are about equally efficient, in case any of you were wondering. It's worth remembering that there are some kinds of problems that packet-filtering firewalls are not best suited for. There's reasonably good information in: "Network (in)security through packet filtering" ftp://ftp.greatcircle.com/pub/firewalls/pkt_filtering.ps.Z ------------------------------ The cisco boot process From: Question 15 Date: 26 July 1994 What really happens when a cisco router boots, from boot start to live interfaces? First it boots the ROM os version. It reads the config. Now, it realizes that you want to netboot. It loads the netbooted copy in on top of itself. It then re-initializes the box and re-reads the config. Manly, yes, but we like it too.... [[ Ummm... in particular it loads the netbooted copy in as WELL as itself,