Both spokes use mGRE tunnel

feroz syed · ‎05-07-2015

hi,

i have been working in this topology from past 10 days. i am using ios code (C7200-ADVENTERPRISEK9-M), Version 15.2(4)M2.

Now the problem is am using phase 2 mode and i read many documents that phase 2 don't support summarization and default-routing are not supported .

In my lab am facing some weird problem which is i can able to do summarize on Hub router, i don't know weather am doing it right or wrong because am totally new to dmvp tech.

here is the hub and spokes config

HUB

R2#sh run int tun 0
Building configuration...

Current configuration : 313 bytes
!
interface Tunnel0
ip address 192.168.1.2 255.255.255.0
no ip redirects
no ip next-hop-self eigrp 1
no ip split-horizon eigrp 1
ip nhrp map multicast dynamic
ip nhrp network-id 2
ip summary-address eigrp 1 0.0.0.0 0.0.0.0
tunnel source FastEthernet1/0
tunnel mode gre multipoint
tunnel key 112111
end

Spoke

R4#sh run int tun 0
Building configuration...

Current configuration : 277 bytes
!
interface Tunnel0
ip address 192.168.1.4 255.255.255.0
no ip redirects
ip nhrp map multicast 200.0.209.2
ip nhrp map 192.168.1.2 200.0.209.2
ip nhrp network-id 4
ip nhrp nhs 192.168.1.2
tunnel source FastEthernet0/0
tunnel mode gre multipoint
tunnel key 112111

R4#sh ip route eigrp
Gateway of last resort is 192.168.1.2 to network 0.0.0.0

D* 0.0.0.0/0 [90/26882560] via 192.168.1.2, 04:33:12, Tunnel0
192.168.3.0/32 is subnetted, 1 subnets
D 192.168.3.3 [90/156160] via 192.168.34.3, 04:36:32, FastEthernet1/0

Sajid Ahmed Khan · ‎05-07-2015

Both spokes use mGRE tunnel encapsulation mode, and the hub sets the originating router next-hop IP address in “reflected” EIGRP updates (by default EIGRP sets the next-hop field to “0.0.0.0” – that is, to self).

So far about NHRP Phase 2 and CEF. Firstly, this mode requires all the spokes to have complete routing information with the next-hop preserved. This may limit scalability in large networks, since not all spokes may accept full load of routing updates. Secondly, CEF only resolve the next-hop information via NHRP, not the full routing prefixes. Actually, the second feature directly implies the first limitation. As noted, the no ip next-hop-self eigrp 123 command is required to make spoke-to-spoke tunnels work with CEF.

DMVPN Phase 2