08-10-2018 09:07 AM
All,
I have a Cisco 3850 fiber switch with a single 10G link to a Cisco Nexus 7009 ("N7K"). The N7K links to the fiber switch's Te1/0/12. What I am seeing in the CDP table is switch2 and switch6 are also showing up via Te1/0/12. Switch2 is on Te1/0/7 and Switch6 is on Te1/0.2. In the CDP table below you can see the correct CDP entires as well as duplicate entires for Switch2 and Switch6 both coming off of Te1/0/12 where the N7K is.
My question is, what could be causing these duplicate entires for switch2 and switch6?
Thank you much,
M. Whitlow
3850fiberswitch#sho cdp neighbors
Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge
S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,
D - Remote, C - CVTA, M - Two-port Mac Relay
Device ID Local Intrfce Holdtme Capability Platform Port ID
nexus7009(JPG20130099)
Ten 1/0/12 178 R S I C N7K-C7009 Eth 4/19
switch1
Ten 1/0/4 143 S I WS-C3850- Gig 1/1/1
switch2
Ten 1/0/7 153 S I WS-C3850- Gig 1/1/1
switch2
Ten 1/0/12 153 S I WS-C3850- Gig 1/1/1
switch3
Ten 1/0/1 153 S I WS-C3850- Gig 1/1/3
switch4
Ten 1/0/6 130 S I WS-C3750G Gig 1/0/12
switch5
Ten 1/0/5 156 S I WS-C3750G Gig 1/0/12
switch6
Ten 1/0/2 128 S I WS-C3850- Gig 1/1/1
switch6
Ten 1/0/12 128 S I WS-C3850- Gig 1/1/1
switch7
Ten 1/0/11 160 S I WS-C3560- Gig 0/1
switch8
Ten 1/0/3 148 S I WS-C3850- Gig 1/1/1
Total cdp entries displayed : 11
08-13-2018 06:55 AM
Few possibilities
1. You may have a hub between the 3850 and the N7K. This hub maybe connected to other switches hence you see the CDP neighbors. You can prove/disprove this theory by tracing the physical path. I doubt this would be the case but again rule out the obvious before looking into a weird behavior.
2. Maybe it is due to https://bst.cloudapps.cisco.com/bugsearch/bug/CSCva55550/?reffering_site=dumpcr
3. If 2 doesn't apply then you maybe getting rogue CDP packets on the interface te1/0/12 for reasons unknown. I would span the interface on both ends to check what 7K is sending and what the 3850 is receiving. With this data open a TAC case to help triage further.
Thanks,
Raj
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide