Yes, it's true that when you ping your own serial interface, the ping actually crosses the serial link! You can also see evidence of it by enabling debugging on the other side.
When I first saw this documented on a Cisco page, I submitted a documentation bug report. :-) I guess it's the only way you'll get a response? It seems awfully weird though... Priscilla p b wrote: > > > Found this a bit unusual... have a feel for why it works > this way, but figured I'd float this to the list for > thoughts... > > Got two routers connected via a serial interface. > > R1 is assigned 192.168.2.1/30 on its serial > R2 is assigned 192.168.2.2/30 on its serial > > On R1, do a "debug ip icmp" > > And then from R1, do a "ping 192.168.2.1" (the IP on > it's local serial interface). > > Interestingly we see the following: > > r2511#ping 192.168.2.1 > > Type escape sequence to abort. > Sending 5, 100-byte ICMP Echos to 192.168.2.1, timeout is 2 > seconds: > !!!!! > Success rate is 100 percent (5/5), round-trip min/avg/max = > 68/73/84 ms > r2511# > 01:35:35: ICMP: redirect rcvd from 192.168.2.2 -- for > 192.168.2.1 use gw 192.168.2.1 > 01:35:35: ICMP: echo reply sent, src 192.168.2.1, dst > 192.168.2.1 > 01:35:35: ICMP: echo reply rcvd, src 192.168.2.1, dst > 192.168.2.1 > 01:35:35: ICMP: echo reply sent, src 192.168.2.1, dst > 192.168.2.1 > 01:35:35: ICMP: echo reply rcvd, src 192.168.2.1, dst > 192.168.2.1 > 01:35:36: ICMP: echo reply sent, src 192.168.2.1, dst > 192.168.2.1 > 01:35:36: ICMP: echo reply rcvd, src 192.168.2.1, dst > 192.168.2.1 > 01:35:36: ICMP: echo reply sent, src 192.168.2.1, dst > 192.168.2.1 > 01:35:36: ICMP: echo reply rcvd, src 192.168.2.1, dst > 192.168.2.1 > 01:35:36: ICMP: echo reply sent, src 192.168.2.1, dst > 192.168.2.1 > 01:35:36: ICMP: echo reply rcvd, src 192.168.2.1, dst > 192.168.2.1 > > Two items of interest: > > 1) The router, when pinging it's local IP, actually transmits > the packets onto the interface with source and destination being > the interface's local IP address. The packets aren't looped > internally, as I would have expected, but are looped via the > remote router. > > 2) Router R2 sends an ICMP redirect suggesting a > more efficient way to reach 192.168.2.1. > > > Interesting behavior.... > > > > > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71401&t=71391 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
