Regarding EIGRP Authentication

[surendrasinghtanwar667]

"Can EIGRP be configured on a per-neighbor basis, or is it strictly an interface-level configuration? I understand that EIGRP authentication is applied to all neighbors on a given interface, which can be limiting in multi-access networks. If I need different authentication settings for specific neighbors, what strategies can I use? Additionally, I’ve heard about key chains that allow for multiple keys, but can these keys be allocated to different routers individually? How does this all relate to the use of virtual templates in my configuration?"

[paul driver]

Hello
Eigrp authentication is on a per interface basis, be it in classic or named modes - meaning that eigrp packet exchanges will be authenticated. between neighbours through interfaces with eigrp applied

As MD5 authentication is not to be used anymore due to vulnerabilities so the more secure hmac-sha authentication is recommended, which can only be applied through named eigrp mode applied to either the default eigrp address family interface that will enable authentication to all eigrp interfaces or via a specific address family interfaces which will naturally enable authentication just on that interface.

router eigrp EIGRP
address-family ipv4 unicast autonomous-system x
af-interface default
authentication mode hmac-sha-256
or
af-interface xxx
authentication mode hmac-sha-256

[MHM Cisco World]

I think he ask if authc per interface or per neighbor.

@surendrasinghtanwar667 it per interface' you can not config different authc for each neighbor reach via same interface (in case you connect more than one router to SW).

MHM

[paul driver]

Hello @MHM Cisco World 
FYI - i did state it was per interface 

[surendrasinghtanwar667]

Oh, I see. However, setting up authentication for each interface might be a challenging task. During my investigation, I came across the concept of a virtual template; could you kindly inform me of this?

[MHM Cisco World · Accepted solution]

EIGRP Authentication per Neighbor (networklessons.com) <<- I think you talking about this 
this friend is not relate to authc per neighbor,
in link he use frame relay and hence can use one virtual interface for each neighbor and add authc under the virtual interface, in end you will also use one virtual interface per neighbor AND authc per interface.

MHM 

[surendrasinghtanwar667]

It was misunderstanding by myside actually i thought that was router basic authentication but my question was what is this virtual interface and how it help to manage specific key for a neighbor which is mentioned in the above article

[paul driver]

Hello
-lol - as i have stated its STILL per interface authentication

[surendrasinghtanwar667]

Hello first read the chat what exactly i am asking about ??  EIGRP Authentication per Neighbor (networklessons.com) 

about this article i have understand that its per interface authentication 

[paul driver]

Hello
Even if you have multi-access network running eigrp then yes authentication is "per neighbour" so to speak due to the individual p2p connections  but it still needs to be applied on there interface where the neighbour resides be it physical or logical.

[balaji.bandi]

I recently deployed some router different requirement, if the only Cisco device that is ok with EIGRP, if different vendor i suggest to OSPF

but the work i did for Cisco Routers only below guide help you :

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_eigrp/configuration/15-mt/ire-15-mt-book/ire-sha-256.pdf