Cisco ASR 900 Ethernet flow point(Bridge domain): Enabling CDP -2

Cisco discovery protocol(CDP) is very important while configuration and troubleshooting the network. In most of the Network devices nowadays, CDP is disabled by default because of security reasons and you need to enable it manually. Enabling CDP is easy and it doesn’t take much, however when CDP needs to be enabled on EFP(ethernet flow point) then it takes some more configuration. In this blog we are going to see CDP configuration on ASR900 devices over the EFP interfaces.

 

Service instance bridge domain
Cisco Discovery protocol(CDP)

 

The above network setup is same as my previous blog (please refer this for device config). We have ASR903 and 920 configured with EFP 20 which is used to tag traffic with 802.1q header. Lets check if we have CDP neighbor in this setup.

ASR920#show 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

Total cdp entries displayed : 0
ASR920#
ASR903#show 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

Total cdp entries displayed : 0
ASR903#

Now in order to enable CDP on EFP we need to do following configurations:

  1. Enable cdp globally on the router.
  2. Enable cdp on physical interface.
  3. configure an untagged EFP under the service instance. Make sure you configure EFP other than EFP 1. Like in my case I have configured EFP 3999.
  4. Enable l2protocol peering for CDP.

 

ASR903(config)#cdp run
!
ASR903#show run int gigabitEthernet 0/1/0
Building configuration...
Current configuration : 302 bytes
!
interface GigabitEthernet0/1/0
no ip address
negotiation auto
cdp enable
service instance 20 ethernet
encapsulation dot1q 20
rewrite ingress tag pop 1 symmetric
bridge-domain 20
!
service instance 3999 ethernet
encapsulation untagged
l2protocol peer cdp
!
end

 

Note : The above configuration needs to be there on both the routers i.e. on ASR920 as well.

Now lets check CDP neighbor.

ASR903#show 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
ASR920    Gig 0/1/0       178     R I      ASR-920-2   Gig 0/0/1

Total cdp entries displayed : 1
ASR903#

Great!! we got the CDP neighbor.


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