04-16-2013 01:12 PM - edited 03-07-2019 12:51 PM
We have the following configuration:
router --> switchA --> switchB
Cisco 3845 router
=============
int gi0/0 --> connected to our WAN
int gi0/1 --> connected to our local network
int gi0/1.8 --> local network sub-interface
encap dot1q 8
ip address 10.10.8.1
Cisco 2960 switch (switchA)
=====================
int gi1/0/49
switchport mode trunk
!
int gi1/0/50
switchport mode trunk
!
vlan 1
vlan 8
!
Cisco 2960 switch (switchA)
=====================
int gi1/0/49
switchport mode trunk
!
vlan 1
vlan 8
!
Router
=====
int gi0/0 is connected to our WAN
int gi0/1 is connected to the 2960 switch (switchA)
Switch A
=======
int gi1/0/49 is connected to the router
int gi1/0/50 is connected to switchB
Switch B
=======
int gi1/0/49 is connected to switchA
If we run the command CDP NEIGHBORS on the router, all we see are devices on the other side of int gi0/0 (WAN link) and nothing on the local network (switchA)
If we run the command CDP NEIGHBORS on switchA we see the router and switchB
We have looked at the configuration on the router and switches and cannot figure out why the router does not see any local devices using the CDP NEIGHBORS command. Tried CDP RUN on the router and CDP ENABLE on int gi0/1 and gi0/1.8.
Any thoughts here?
Solved! Go to Solution.
04-16-2013 02:02 PM
I think this is due to the fact that CDP is carried in VLAN 1, and there's no sub-interface with VLAN 1 on the router.
Regards
Sent from Cisco Technical Support Android App
04-16-2013 01:18 PM
Hi Dtom,
Can you please paste show version from all 3 devices?
Kind regards,
--
Paul Preston
Proxar IT Ltd. Registered in England and Wales: 6744401- VAT: 942985479
Tubs Hill House, London Road, Sevenoaks, Kent, TN13 1BL
Tel: (+44) 0844 809 4335
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Email: paul.preston@proxar.co.uk
04-16-2013 01:19 PM
On the router issue "clear cdp table" and test again.
If not, plug and unplug the physical link and test.
HTH
04-16-2013 01:48 PM
Check to see if the trunk link from Switch A to the 3845 is configured for dot1q encapsulation, it may be set to ISL:
show int trunk
If it is ISL, then at the interface change it to dot1q
switchport trunk encapsulation dot1q
Sent from Cisco Technical Support iPhone App
04-16-2013 02:02 PM
I think this is due to the fact that CDP is carried in VLAN 1, and there's no sub-interface with VLAN 1 on the router.
Regards
Sent from Cisco Technical Support Android App
04-17-2013 01:27 PM
That was it. the sub-interface with Vlan1 was shutdown. Thank.
04-17-2013 03:50 PM
Happy to be of assistance
Regards
Sent from Cisco Technical Support iPhone App
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