From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Tue Dec 21 2004 - 13:46:01 GMT-3
Bola,
Take the below example. R1 and R2 run EIGRP and peer via EBGP.
A prefix is first injected into EIGRP, then the same prefix is injected
into BGP.
Before route is injected into BGP:
R1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
2.0.0.0/32 is subnetted, 1 subnets
D 2.2.2.2 [90/409600] via 12.0.0.2, 00:00:04, Ethernet0/0
C 12.0.0.0/8 is directly connected, Ethernet0/0
R1#show ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(12.0.0.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 2.2.2.2/32, 1 successors, FD is 409600
via 12.0.0.2 (409600/128256), Ethernet0/0
P 12.0.0.0/8, 1 successors, FD is 281600
via Connected, Ethernet0/0
R1#
In the above output we can see the prefix 2.2.2.2/32 is learned via
EIGRP and has a feasible distance of 409600. Now the prefix is injected
into BGP on R2, and the administrative distance of 20 vs 90 will cause
the BGP route to be installed on R1 instead of EIGRP.
R1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS
inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [20/0] via 12.0.0.2, 00:00:18
C 12.0.0.0/8 is directly connected, Ethernet0/0
R1#show ip eigrp topology
IP-EIGRP Topology Table for AS(1)/ID(12.0.0.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 2.2.2.2/32, 0 successors, FD is Inaccessible
via 12.0.0.2 (409600/128256), Ethernet0/0
P 12.0.0.0/8, 1 successors, FD is 281600
via Connected, Ethernet0/0
Now 2.2.2.2/32 is installed via BGP. Since the route is not installed
via EIGRP the feasible distance is now Inaccessible (infinite metric).
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
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> -----Original Message-----
> From: Adebola Adegbonmire [ MTN - UBA ]
[mailto:AdebolaA@mtnnigeria.net]
> Sent: Tuesday, December 21, 2004 4:58 AM
> To: Brian McGahan; Vijaybhasker.Vuppala2@ge.com; ccie2004@excite.com;
> ccielab@groupstudy.com
> Subject: RE: EIGRP Topology Table
>
> Brian,
> You say ". Routes in the EIGRP topology that are not installed in
> the IP routing table have a feasible distance of inaccessible"
> But if I have a route for same route in the table via BGP it won't be
> advertised to neighbour I understand, what I do not understand is your
> referring to all routes not installed in table as having an
inaccessible
> feasible distance is that so?
>
> Bola
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Brian
> McGahan
> Sent: 21 December 2004 04:54
> To: Vijaybhasker.Vuppala2@ge.com; ccie2004@excite.com;
> ccielab@groupstudy.com
> Subject: RE: EIGRP Topology Table
>
> This is correct. Routes in the EIGRP topology that are not installed
in
> the IP routing table have a feasible distance of inaccessible
> (infinite). This means, like a metric of 16 in RIP, that the route is
> not used nor is it advertised onto other neighbors.
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
> 24/7 Support: http://forum.internetworkexpert.com
> Live Chat: http://www.internetworkexpert.com/chat/
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Vijaybhasker.Vuppala2@ge.com
> > Sent: Monday, December 20, 2004 9:11 PM
> > To: ccie2004@excite.com; ccielab@groupstudy.com
> > Subject: RE: EIGRP Topology Table
> >
> > If a route to a subnet is available in the topology table but is not
> > installed in routing table for some reason (Eg: router has another
> route
> > to
> > the same subnet with better admin distance like static route) it
> doesn't
> > propogate/advertise the EIGRP route to it's neighbour...
> >
> > Others group members....correct me if i'm wrong....
> >
> > -----Original Message-----
> > From: Ned [mailto:ccie2004@excite.com]
> > Sent: Monday, December 20, 2004 8:44 PM
> > To: ccielab@groupstudy.com
> > Subject: EIGRP Topology Table
> >
> >
> > Hi, was just reading up on some eigrp and had a doubt which I am
sure
> > most
> > of you know the answers too. When viewing the show ip eigrp topology
> table
> > on a router what routes will I see in the table?Will all routes that
I
> see
> > in a neighboring routers topology table show up in this routers
> topology
> > table even though the neighbor might not be using that route in the
> > routing
> > table.So I think my question goes back to where if the route is not
> being
> > used by a router will it advertise that route to its neighbors?
Thnks
> for
> > your help.
> >
> > _______________________________________________
> > Join Excite! - http://www.excite.com
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> >
> >
>
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