From: Jared Scrivener (jscrivener@ipexpert.com)
Date: Sat Jan 31 2009 - 17:21:10 ARST
Hey Hobbs,
It appears that your switch is copying ALL frames (from layer 2) received
via R2 and outputting them to R5. That includes CDP frames.
R5 thinks that R2 is a CDP neighbor as a result of this. CDP adjacencies
require duplex to be matching (as they assume that CDP adjacencies are on
the same physical link) but it appears that R2 is half-duplex. This is
giving you CDP errors.
My first question is "why" are you doing this (spanning a router to another
router), but I'm sure you're doing it to learn something new. :)
Just disable CDP on R2's interface and your issue should resolve itself
(assuming changing the duplex on R2 doesn't help).
Cheers,
Jared Scrivener CCIE3 #16983 (R&S, Security, SP), CISSP
Technical Instructor - IPexpert, Inc.
Telephone: +1.810.326.1444
Fax: +1.810.454.0130
Mailto: jscrivener@ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Hobbs
Sent: Saturday, 31 January 2009 2:02 PM
To: Cisco certification
Subject: RSPAN causing an l2protocol tunnel-like effect
Hello,
I have the following:
R5---sw1---sw2---R2
Afetr setting up RSPAN on the switches (3560s), sw1 sees R2 as a CDP
neighbor.
I have a monitor session on sw2 destined for a remote vlan as follows:
SW2#sho run | inc mon
monitor session 1 source interface Fa0/2
monitor session 1 destination remote vlan 999
On sw1 I start getting these messages:
00:50:32: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/13 (not half duplex), with R2 Ethernet0/0 (half duplex).
00:51:32: %CDP-4-DUPLEX_MISMATCH: duplex mismatch discovered on
FastEthernet0/13 (not half duplex), with R2 Ethernet0/0 (half duplex).
Sure enough, Sw1 now sees R2 as a cdp neighbor on the port connected to sw2
SW1#sho cdp ne | inc 0/13
SW2 Fas 0/13 125 R S I
WS-C3560-2Fas 0/13
R2 Fas 0/13 165 R S I 3640
Eth 0/0
fyi, sw1 has the following config:
SW1#sho run | inc mon
monitor session 1 destination interface Fa0/5 ingress untagged vlan 100
monitor session 1 source remote vlan 999
I have define vlan 999 as a remote-span vlan.
Any ideas?
thank you
Blogs and organic groups at http://www.ccie.net
This archive was generated by hypermail 2.1.4 : Sun Mar 01 2009 - 09:43:41 ARST