EIGRP authentication on GRE tunnel interface?

Question

I want to implement authentication on EIGRP updates.

Can I enable EIGRP authentication on a GRE tunnel interface instead of physical interface?

Answer 1

Yes, you can do that. Below is an example:

Router-A#
!
key chain Netlab
 key 13
   key-string Netlabbuilder
!
interface Tunnel1
 description Site-B
 ip address 10.99.99.1 255.255.255.252
 ip mtu 1400
 ip authentication mode eigrp 10 md5
 ip authentication key-chain eigrp 10 Netlab
 ip tcp adjust-mss 1360
 cdp enable
 tunnel source 13.1.87.2
 tunnel destination 10.12.85.2
end
!
Router-A#show ip eigrp neighbors tunnel 1
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
1   10.99.99.2              Tu1               13 00:04:38   54  5000  0  17

#####

Router-B#
!
key chain Netlab
 key 13
   key-string Netlabbuilder
!
interface Tunnel1
 description Site-A
 ip address 10.99.99.2 255.255.255.252
 ip mtu 1400
 ip authentication mode eigrp 10 md5
 ip authentication key-chain eigrp 10 Netlab
 ip tcp adjust-mss 1360
 cdp enable
 tunnel source 10.12.85.2
 tunnel destination 13.1.87.2
end
!
Router-B#show ip eigrp neighbors tunnel 1
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   10.99.99.1              Tu1               13 00:05:55  212  5000  0  10