nanog mailing list archives
Re: The use of .0/.255 addresses.
From: Jon Lewis <jlewis () lewis org>
Date: Sun, 27 Jun 2004 15:41:28 -0400 (EDT)
On Sun, 27 Jun 2004, Stephen J. Wilcox wrote:
Hi Jon, I currently have a few .255/32s with Cisco and Foundry products and have various windows/linux/OSX machines that access them without problems..
I'm pretty confident this is a classful/classless bug in 12.1T. I just got into the customer's router that was sending what looked like replies to a broadcast ping, and that's just what it was. Here's the output from debug ip packet on the CPE that was replying when I pinged 209.208.6.255 from the 7206. IP: s=209.208.6.xyz (Serial0.2), d=255.255.255.255, len 100, rcvd 2 IP: s=209.208.6.xyz (Serial0.2), d=255.255.255.255, len 100, rcvd 2 IP: s=209.208.6.xyz (Serial0.2), d=255.255.255.255, len 100, rcvd 2 Checked with an ACL on the input side of the CPE's serial subint, *Mar 3 08:40:19: %SEC-6-IPACCESSLOGDP: list test permitted icmp 209.208.6.xyZ (Serial0.2 DLCI 100) -> 255.255.255.255 (0/0), 1 packet where 209.208.6.xyz is the customer's serial IP, and 209.208.6.xyZ is the 7206's serial IP. Both ends to have no ip directed-broadcast.
I found some time ago that my home DSL connected network could not reach (telnet, ping, etc.) that router's loopback. Our monitoring system could, and several iBGP peers could, so I didn't notice the issue until one night when trying to do some work from home.I could see the problem with DSL's where the provider may be interfering.. surprised about your monitoring tho...
No...I said the monitoring system didn't have a problem with it. It fortunately doesn't have to transit the affected router which only handles T1 & DSL aggregation (including my home DSL).
#sh ip ro 209.208.6.255 Routing entry for 209.208.6.255/32 Known via "ospf 1", distance 110, metric 20, type extern 2, forward metric 4 Last update from 209.208.16.29 on FastEthernet0/0.1, 00:46:47 ago Routing Descriptor Blocks: * 209.208.16.29, from 209.208.6.255, 00:46:47 ago, via FastEthernet0/0.1 Route metric is 20, traffic share count is 1
#sh ip cef 209.208.6.255 209.208.6.255/32, version 12215105, cached adjacency 209.208.16.29 0 packets, 0 bytes tag information set, shared local tag: 398 fast tag rewrite with Fa0/0.1, 209.208.16.29, tags imposed: {114} via 209.208.16.29, FastEthernet0/0.1, 0 dependencies next hop 209.208.16.29, FastEthernet0/0.1 valid cached adjacency tag rewrite with Fa0/0.1, 209.208.16.29, tags imposed: {114} #sh tag-switching forwarding-table 209.208.6.255 detail Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 398 114 209.208.6.255/32 0 Fa0/0.1 209.208.16.29 MAC/Encaps=18/22, MTU=1520, Tag Stack{114} 0001638B90000005DC493400810000018847 00072000 No output feature configured Per-packet load-sharing It knows the next hop is another 7206 with connections to the rest of our network. Why is it sending this out as a broadcast ping instead of routing (tag switching) it? I know...wrong list. I'll ask on cisco-nsp, but the operational lesson here is that it's not just the junk from Redmond that may have classful/classless IP routing issues. Even your core routers might, depending on IOS versions. ---------------------------------------------------------------------- Jon Lewis | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
Current thread:
- The use of .0/.255 addresses. Jonathan McDowell (Jun 26)
- Re: The use of .0/.255 addresses. Peter Corlett (Jun 26)
- Re: The use of .0/.255 addresses. Tony Li (Jun 26)
- Re: The use of .0/.255 addresses. Jon Lewis (Jun 26)
- Re: The use of .0/.255 addresses. Stephen J. Wilcox (Jun 27)
- Re: The use of .0/.255 addresses. Peter Corlett (Jun 27)
- Re: The use of .0/.255 addresses. Stephen J. Wilcox (Jun 27)
- Re: The use of .0/.255 addresses. Iljitsch van Beijnum (Jun 27)
- Re: The use of .0/.255 addresses. Paul Jakma (Jun 27)
- Re: The use of .0/.255 addresses. Paul Jakma (Jun 27)
- Re: The use of .0/.255 addresses. Jon Lewis (Jun 26)
- Re: The use of .0/.255 addresses. Jon Lewis (Jun 27)
- Re: The use of .0/.255 addresses. william(at)elan.net (Jun 26)
- Re: The use of .0/.255 addresses. Howard C. Berkowitz (Jun 26)
- Re: The use of .0/.255 addresses. sthaug (Jun 27)
- Re: The use of .0/.255 addresses. Petri Helenius (Jun 27)
- Re: The use of .0/.255 addresses. Stephen Sprunk (Jun 27)
- <Possible follow-ups>
- RE: The use of .0/.255 addresses. Chris Ranch (Jun 26)
- Re: The use of .0/.255 addresses. Jonathan McDowell (Jun 27)
- RE: The use of .0/.255 addresses. Tony Hain (Jun 28)
- Re: The use of .0/.255 addresses. Jonathan McDowell (Jun 27)