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Wednesday, May 30, 2012

How do you configure ERSPAN Between Two Routers

We are trying to mirror traffic from one router to another with below config:
R1#sh run | sec monitor
monitor session 1 type erspan-source
source interface Gi0/0/3 rx
  erspan-id 100
  ip address
  origin ip address
R11#sh monitor session all
Session 1
Type                   : ERSPAN Source Session
Status                 : Admin Enabled
Source Ports           :
    RX Only            : Gi0/0/3
Destination IP Address :
Destination ERSPAN ID  : 100
Origin IP Address      :
R2#sh run | sec monitor
monitor session 1 type erspan-destination
destination interface Gi0/0/4
  erspan-id 100
  ip address
R2#sh monitor session all
Session 1
Type                   : ERSPAN Destination Session
Status                 : Admin Enabled
Destination Ports      : Gi0/0/4
Source IP Address      :
Source ERSPAN ID       : 100
R2#sh platform hardware qfp active feature erspan state
  Status    : Active
  Complexes : 1
  CPPs      : 1
  Max sessions : 1024
  Max outputs  : 128
  Encaps type  : ERSPAN type-II
  GRE protocol : 0x88BE
  MTU          : 1464
  IP TOS       : 0
  IP TTL       : 255
  COS          : 0
System Statistics:
  DROP src session replica  :                  0 /                  0
  DROP term session replica :                  0 /                  0
  DROP receive malformed    :                  0 /                  0
DROP receive invalid ID   :           24321174 /        21427043334
  DROP recycle queue full   :                  0 /                  0
  DROP no GPM memory        :                  0 /                  0
  DROP no channel memory    :                  0 /                  0
Client Debug Config:
  Enabled: Info, Warn
Data Path Debug Config:
Note: is R2's loopback. is R1's loopback.
The configuration seems OK and traffic was mirror from R1 to R2 but it was dropped at R2 with DROP receive invalid ID increasing.

The ERSPAN-Destination session should have the Source IP Address as the IP address ( and not the Origin IP Address which you have configured.

ip address in destination session and ip address in source session should match. If they don't- that is causing the drops you see.

Please try the following:
- remove both sessions completely
- configure both with new session id - e.g. 101
- configure "ip address" in source and destination sessions to be
- have "plim ethernet vlan filter disable"command on outgoing interface

For "plim ethernet vlan filter disable" - it is used to disable filter for packets tagged with VLAN as by default ASR drop them in older versions.

Citation - This blog post does not reflect original content from the author. Rather it summarizes content that are relevant to the topic from different sources in the web. The sources might include any online discussion boards, forums, websites and others.


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