I have setup one IPv6 6to4 tunnel between two routers.The tunnel seems to be up and running and I'm able to ping from Router R1 to R2 as well.

However,I would like mirror the WAN port to see the packet structure in wireshark. I don't have a L2/l3 managed switch with me now.How can I mirror the WAN port traffic to one of the port in router itself? say (WAN) FE4 to (LAN)FE0?

  • The firmware in those devices is basic at best, if it were me id just put a cheap hub in place to look at the traffic flows, other alternative is use a network TAP, but those can be rather expensive. Regards John
    – John Ellis
    Nov 28, 2017 at 8:10
  • Normally I used to use an open-wrt based router to mirror ports or a 10mbps hub.However,Hub has become an antique piece these days! I wanted to know whether it is possible to do it in the router itself to avoid digging up a hub from our inventory. Appreciate your reply John.
    – Maverick
    Nov 28, 2017 at 8:29
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide and accept your own answer.
    – Ron Maupin
    Feb 19, 2018 at 20:14

1 Answer 1


You can't do it with Cisco 871 itself. You can try re-configure your router to receive your ISP on one of switch ports and then setup SPAN session from this port to another.

(config)# monitor session 1 source interface fa3 both
(config)# monitor session 1 destination interface fa0
  • Let me try this Andrey :)
    – Maverick
    Nov 28, 2017 at 8:30
  • @RenoldSingh hello! did you get desired result? Nov 29, 2017 at 11:46
  • It didn't worked.I bought a TPlink SG108E Smart switch to do the mirroring.
    – Maverick
    Dec 20, 2017 at 7:19

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