What are some methods for conserving IP addresses for serial lines? From: Question 38 Date: 22 April 1996 VLSM and unnumbered point to point interfaces are the obvious ways. The 'ip unnumbered' subcommand indicates another interface or sub-interface whose address is used as the IP source address on messages that the router originates on the unnumbered interface, such as telnet or routing messages. By doing this, the router is reachable for management purposes (via the address of the one numbered interface) but consumes no IP addresses at all for its unnumbered links. When a serial ip interface connects several sites, as an SMDS link might, then the use of an appropriate subnet mask (and a routing protocol that can make good use of the information) will minimize address consumption. ------------------------------ Why do some ip addresses get rejected? From: Question 39 Date: 23 April 1996 How come my cisco router doesn't accept an address like: "ip address 192.111.107.1 255.255.255.240" or "ip address 171.69.0.1 255.255.0.0" When "subnetting" of IP networks was first sanctioned by the IETF, the first and last subnets (the all zeros subnet and all ones subnet) were reserved for rather obscure uses and because of the confusion that would be caused with routing protocols that don't carry net mask information. It was technically illegal to place hosts or routers on those two subnets. Several hosts and most other vendor's router products have problems operating with the reserved subnets, so their use is discouraged. However, in 1995, the IETF removed the restrictions on the use of these reserved subnets as part of the classless routing effort. If you would like to use the reserved subnets, simply add the line "ip subnet-zero" to your cisco configuration. You might consider adding "ip subnet-zero" to all your configurations as a metter of course, to avoid being bitten by this in the future. ------------------------------ How do 4xxx serial numbers correspond to models? From: Question 40 Date: 27 April 1996 show version serial # Label ------------------------------------------------------- 4000 Rev A0 440xxxxx C4000 4000M Rev B0 445xxxxx C4000 4500 450xxxxx C4500 4500M 455xxxxx C4500 4700 470xxxxx C4700 ------------------------------ Where can I find more info on TACACS+ From: Question 41 Date: 28 April 1996 In addition to sundry cisco documentation and ftp-able info, there exists a TACACS+ mailing list. For more information, see http://www.disaster.com/tacplus/. ------------------------------ Acknowledgements. From: Question 99 Date: 19 May 1995 The following people contributed to this FAQ, and their contributions are greatly appreciated, both questions and answers (in alpha order): Arpakorn Boonkongchuen Robert Kiessling "Ronnie B. Kon" Alain Martineau Barton.Bruce@camb.com (Barton F. Bruce / CCA) Bill Miskovetz Charley Kline Dave Katz Eriks Rugelis Howard C. Berkowitz, PSC International, Jim Forster John Wright Pete Siemsen Phillip Remaker Ran Atkinson Robert Kiessling Sanjay Rungta~ Sean McGrath Srinivas Vegesna Steve Cunningham Warren Lavallee William "Chops" Westfield atkinson@sundance.itd.nrl.navy.mil (Ran Atkinson) bpinsky@cisco.com (Bruce Pinsky) buk@taz.de ($ Burkhard Kohl) fred@cisco.com (Fred Baker) jerry@ksu.ksu.edu (Jerry Anderson) jhawk@panix.com (John Hawkinson) john@cisco.com (John Wright) john@gulfa.ods.gulfnet.kw (John Temples) paul@hawksbill.sprintmrn.com (Paul Ferguson) peter@ulisse.rhein-main.de (Peter Radig) tli@cisco.com (Tony Li) tom@park.uvsc.edu (Thomas R. Kimpton) vikas@Tudor.Com (Vikas Aggarwal) warner@cats.ucsc.edu (Jim Warner)