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Ask Me Anything - Configuration, Verification, and Troubleshooting of Dynamic Routing Protocols

Community Manager
Community Manager

This topic is a chance to clarify your questions about the configuration, verification, troubleshooting and general best current practices of dynamic routing protocols. All questions regarding to general design, flooding, in-depth mechanics, and features of RIP, OSPF, IS-IS EIGRP, and BGP are welcome.

Dynamic routing protocols are a fundamental piece for internetworking, their main function is to provide the mechanisms to generate, process, and distribute topological and network layer reachability information (NLRI). Having an in-depth knowledge of routing protocols is key to understand modern overlay solutions such as Cisco DNA and a plethora of SDN designs, since these use some form of underlying routing form to perform connections under the hood.

To participate in this event, please use the Join the Discussion : Cisco Ask the Expertbutton below to ask your questions

Ask questions from Monday 09th to Friday 20th of December, 2019

Featured expert
elvin.jpgElvin Arias is a devoted IP routing learner with a wide knowledge and experience in different technologies such as MPLS, x-EVPN, Segment Routing, IS-IS, MP-BGP, Network Programmability and Automation. He works as a Network Development Engineer in the Internet Edge Engineering team at Amazon in the EMEAR region, he focuses on Automation and R&S/SP technologies. Before that, he worked as a senior TAC engineer in the Service Provider team for the Americas theatre at Cisco. Elvin is an active member of the networking community where he often collaborates developing and publishing technical content or participating on live events or forum sessions for R&S and SP technologies for the Cisco Community, as well he engages in technical discussions in the Cisco Learning Networking community, where he has been honored with the Cisco Designated VIP distinction in multiple years 2013-2017. Elvin holds two CCIE certifications, one in R&s and one in SP (#57406)..

Elvin might not be able to answer each question due to the volume expected during this event. Remember that you can continue the conversation on the Routing community.

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Hello Guru's,


How can I discover what vlans are traversing a particular VRF across my wan?  I issued the sh ip route vrf vrfName command and got a ton of subnet ip addresses and physical egress interfaces, but I need to distinguish which vlans are flowing out of this edge router out into the WAN.  Thanks for any help.

Hi telestrial2020,


Thank you for your question!


Regularly this information should be known via an updated network diagram that reflects the connections and indicates what VLANs exist at each point of the network. Network diagrams and flow diagrams will be the sources of information where this is reflected.


If this does not exist, a way is by checking the associated interfaces within the VRF [show vrf / show running-config vrf <VRF>]. You will need to verify the subinterface and observe it on the local router, the subinterface will indicate what is the corresponding encapsulation.

Of course, querying the router using some kind of network management system would be ideal, like Cisco Prime / Prime Infrastructure among others.


As an additional note on this subject, there is also another VRF-to-VLAN application named Easy Virtual Networking Network (EVN), where you can create trunks of VRFs, and via this application, is easier to map and visualise from the local router perspective what VRFs corresponds to each VLAN by the virtue of what is called vnet trunks.


A white paper on this technology can be found here,