RSPAN causing an l2protocol tunnel-like effect

From: Hobbs (deadheadblues@gmail.com)
Date: Sat Jan 31 2009 - 17:01:58 ARST


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

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