Re: EIGRP Neighbours

If the masks are different EIGRP will still build it's peers
Here is a test I did

R1(fa0/0) <-> SW1
SW1 IP ->129.1.17.7/24
R1 IP -> 129.1.17.1/24 -> Neighbourship UP

Change R1 Subnet mask to
Rack1R1(config-if)#int fa0/0
Rack1R1(config-if)#ip address 129.1.17.1 255.0.0.0
Rack1R1(config-if)#
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is down: address changed
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is up: new adjacency

Rack1R1(config-if)#ip address 129.1.17.1 255.255.0.0
Rack1R1(config-if)#
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is down: address changed
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is up: new adjacency

Rack1R1(config-if)#ip address 129.1.17.1 255.255.255.240
Rack1R1(config-if)#
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is down: address changed
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is up: new adjacency
Rack1R1(config-if)#

Rack1R1(config-if)#ip address 129.1.17.1 255.255.255.248
Rack1R1(config-if)#
2d16h: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 200: Neighbor 129.1.17.7
(FastEthernet0/0) is down: address changed
Rack1R1(config-if)#

So it looks like if they are in the same primary subnet, the peers should
form
The only instance where the peer did not form was when the Subnet mask on R1
excluded the host IP on SW1 from the IP range covered by R1

On Sun, Jul 5, 2009 at 11:03 PM, Scott Morris <smorris_at_ine.com> wrote:

> That depends on whether you enjoy the repetitive "Neighbor not on common
> subnet" errors you'll get. :)
>
> You must match.
>
>
>
>
> *Scott Morris*, CCIE/x4/ (R&S/ISP-Dial/Security/Service Provider) #4713,
>
> JNCIE-M #153, JNCIS-ER, CISSP, et al.
>
> JNCI-M, JNCI-ER
>
> evil_at_ine.com
>
>
> Internetwork Expert, Inc.
>
> http://www.InternetworkExpert.com
>
> Toll Free: 877-224-8987
>
> Outside US: 775-826-4344
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>
> Knowledge is power.
>
> Power corrupts.
>
> Study hard and be Eeeeviiiil......
>
>
>
>
>
> hopalong wrote:
> > Hi
> >
> > Can anyone tell when EIGRP attempts to form a relationship, do the two
> > routers have to be in the same subnet? or do they just have to be in the
> > same major network?
> >
> > I seem to have routers that suggest that the second option is correct?
> >
> > Many thanks
> >
> >
> > Blogs and organic groups at http://www.ccie.net
> >
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Received on Mon Jul 06 2009 - 09:39:33 ART