Eigrp variance control

[feroz syed]

hi,

i have only one path to reach router 3 loop int i.e 172.172.172.3. via serial 2/0, the FD distance is 2297856 and  i  try to increase the fd cost to add other another path to reach r3 loop. after i increase the 1000 fd now it change to  2298856.

if i change the variance multiply by 2 or 3 to add other path to reach 172.172.172.3 network, it affect the other routes or it include another path like 2.2.2.2. So how to avoide or manage variance cmd to control specific route

P 172.172.172.3/32, 1 successors, FD is 2297856, serno 30

        via 192.168.10.3 (2297856/128256), Serial2/0

        via 172.16.23.2 (2300416/2297856), FastEthernet1/1

        via 192.168.1.2 (2300416/2297856), FastEthernet1/0

P 172.172.172.3/32, 1 successors, FD is 2297856, serno 38

        via 192.168.10.3 (2298856/128256), Serial2/0

        via 172.16.23.2 (2301416/2297856), FastEthernet1/1

        via 192.168.1.2 (2301416/2297856), FastEthernet1/0

[paul driver]

Hello

varience is for equal or unequal load balancing I think what you are saying is you wish for a least preffered path to take precedence - is this correct if so-

for a specific route you can use an offset list and apply it to the least preffered interface facing the destination.route within the eigrp router process

access-list 10 permit 172.172.172.3 0.0.0.0

router eigrp
offset-list 10 out 1000 faX/X

res
paul



Sent from Cisco Technical Support Android App

[feroz syed]

what about the varinace option it ill affect the other routes too am right ?

[JohnTylerPearce · Accepted solution]

Yes, as far as I know, the variance command will affect all other routes. If I am wrong on this someone, please let me know. Also, what Pdriver suggested about doing an offset-list is a good idea. Remember, since EIGRP is an "Enhanced Distance Vector" protocol, an offset-list would work just fine.

[JohnTylerPearce]

I'm assuming that this is from the perspective of R1. Remember, for a route in EIGRP, to be considerd a Feasible Successor, it MUST meet the Feasbility Conditon, which states that, the Report Distance to a route from a neighbor, MUST be less than the FD of the Successor.

Since this looks like GNS3, to get this going real quick, do a 'show ip eigrp topology', this will show the Topology Database, for the EIGRP next, if the route is a Feasible Successor you will see it here, if not do 'show ip eigrp topology all-links'.

Now, from looking at this...

P 172.172.172.3/32, 1 successors, FD is 2297856, serno 30

        via 192.168.10.3 (2297856/128256), Serial2/0

        via 172.16.23.2 (2300416/2297856), FastEthernet1/1

        via 192.168.1.2 (2300416/2297856), FastEthernet1/0

P 172.172.172.3/32, 1 successors, FD is 2297856, serno 38

        via 192.168.10.3 (2298856/128256), Serial2/0

        via 172.16.23.2 (2301416/2297856), FastEthernet1/1

        via 192.168.1.2 (2301416/2297856), FastEthernet1/0

As you can see above, the FD of the two other routes, do not meet the Feasibility Condition, therefore, they will not be considered for Feasible Successor routes, even if you do 'variance 2, or variance 3'.

What I would do, is make sure the "bold-highlighed routes' meet the Feasibility condition, and the run 'variance 2' under the EIGRP process, on R1, and you should be able to use those routes.

And remember, with loopback interfaces, you will have the cost to get to the router with the loop back, and then the cost from the router itself to the loopback.

I hope this helps some.

[feroz syed]

P 172.172.172.3/32, 1 successors, FD is 2297856, serno 30

        via 192.168.10.3 (2297856/128256), Serial2/0

        via 172.16.23.2 (2300416/2297856), FastEthernet1/1

        via 192.168.1.2 (2300416/2297856), FastEthernet1/0

P 172.172.172.3/32, 1 successors, FD is 2297856, serno 38

        via 192.168.10.3 (2298856/128256), Serial2/0

        via 172.16.23.2 (2301416/2297856), FastEthernet1/1

        via 192.168.1.2 (2301416/2297856), FastEthernet1/0

the reported distance is less then fd  2297856 < 2298856

R1#sh ip eigrp topology

IP-EIGRP Topology Table for AS(1)/ID(192.168.1.1)

Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,

       r - reply Status, s - sia Status

P 3.3.3.3/32, 1 successors, FD is 2298856

        via 192.168.10.3 (2298856/128256), Serial2/0

        via 172.16.23.2 (2301416/2297856), FastEthernet1/1

        via 192.168.1.2 (2301416/2297856), FastEthernet1/0

P 2.2.2.2/32, 2 successors, FD is 157160

        via 172.16.23.2 (157160/128256), FastEthernet1/1

        via 192.168.1.2 (157160/128256), FastEthernet1/0

P 1.1.1.1/32, 2 successors, FD is 157160

        via 172.16.23.2 (157160/128256), FastEthernet1/1

        via 192.168.1.2 (157160/128256), FastEthernet1/0

P 192.168.10.0/24, 1 successors, FD is 2169856

        via Connected, Serial2/0

P 192.168.1.0/24, 1 successors, FD is 28160

        via Connected, FastEthernet1/0

P 192.168.22.0/24, 2 successors, FD is 2173416

        via 172.16.23.2 (2173416/2169856), FastEthernet1/1

        via 192.168.1.2 (2173416/2169856), FastEthernet1/0

        via 192.168.10.3 (2682856/2169856), Serial2/0

P 172.16.23.0/24, 1 successors, FD is 28160

        via Connected, FastEthernet1/1

P 172.172.172.3/32, 1 successors, FD is 2298856

        via 192.168.10.3 (2298856/128256), Serial2/0

        via 172.16.23.2 (2301416/2297856), FastEthernet1/1

        via 192.168.1.2 (2301416/2297856), FastEthernet1/0

Before in this topology i can't see other two path via fa 1/1 and 1/0 after i increase fd it now in route table

R1#sh 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, su - IS-IS summary, 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

     1.0.0.0/32 is subnetted, 1 subnets

D       1.1.1.1 [90/157160] via 192.168.1.2, 03:06:53, FastEthernet1/0

                [90/157160] via 172.16.23.2, 03:06:53, FastEthernet1/1

     2.0.0.0/32 is subnetted, 1 subnets

D       2.2.2.2 [90/157160] via 192.168.1.2, 03:06:53, FastEthernet1/0

                [90/157160] via 172.16.23.2, 03:06:53, FastEthernet1/1

     3.0.0.0/32 is subnetted, 1 subnets

D       3.3.3.3 [90/2298856] via 192.168.10.3, 03:06:53, Serial2/0

                [90/2301416] via 192.168.1.2, 03:06:53, FastEthernet1/0

                [90/2301416] via 172.16.23.2, 03:06:53, FastEthernet1/1

C    192.168.10.0/24 is directly connected, Serial2/0

     172.172.0.0/32 is subnetted, 1 subnets

D       172.172.172.3 [90/2298856] via 192.168.10.3, 03:06:53, Serial2/0

                      [90/2301416] via 192.168.1.2, 03:06:53, FastEthernet1/0

                      [90/2301416] via 172.16.23.2, 03:06:55, FastEthernet1/1

     172.16.0.0/24 is subnetted, 1 subnets

C       172.16.23.0 is directly connected, FastEthernet1/1

D    192.168.22.0/24 [90/2682856] via 192.168.10.3, 03:06:56, Serial2/0

                     [90/2173416] via 192.168.1.2, 03:06:56, FastEthernet1/0

                     [90/2173416] via 172.16.23.2, 03:06:57, FastEthernet1/1

C    192.168.1.0/24 is directly connected, FastEthernet1/0

[paul driver · Accepted solution]

Hello

yes variance be.it for equal.or unequal lb will affect all routes.

res
paul


Sent from Cisco Technical Support Android App

[feroz syed]

am confused

which one should be higher then FD is 2297856  (2301416 fd/2297856 ad)  (2301416 fd /2297856 ad)

Fd or Ad

[JohnTylerPearce]

Feroz,

For a route to be considered as a Feasible Successor and or valid route (Might be the better term), it has to meet the Feasibility Condition.

So the Feasible Distance of the destination-prefix, will need to always be higher than the Reported Distance of possible Feasible Successor routes and or other valid routes for the same destination-prefix.

So if your FD is 2297856, make sure the other routes, have a Reported Distance that is less than that Feasible Distance.

I use the term Reported Distance for Administrative Distance, because, the terms can get confusing. Adminstrative Distance technically has two definitions, depending on in what context you use it.

For example:

(2297856/1200000)

(2297856/2300000)

(2297856/2300000)

Notice how the 2300000 is more than the Feasible Distance, this means you can't use the routes. So make sure that number is less than 2300000.

This means that the other routers with those routes, will ned their Feasible Distance lowered to meet this requirement.

[feroz syed]

Got it, after increasing variance from 1 to 2 now have route to three possible path, but now i have three path to reach 3.3.3.3 which i dont want.

R1#sh ip route                   

     1.0.0.0/32 is subnetted, 1 subnets

D       1.1.1.1 [90/157160] via 192.168.1.2, 00:00:41, FastEthernet1/0

                [90/157160] via 172.16.23.2, 00:00:41, FastEthernet1/1

     2.0.0.0/32 is subnetted, 1 subnets

D       2.2.2.2 [90/157160] via 192.168.1.2, 00:00:41, FastEthernet1/0

                [90/157160] via 172.16.23.2, 00:00:41, FastEthernet1/1

     3.0.0.0/32 is subnetted, 1 subnets

D       3.3.3.3 [90/2298856] via 192.168.10.3, 00:00:41, Serial2/0

                [90/2301416] via 192.168.1.2, 00:00:41, FastEthernet1/0

                [90/2301416] via 172.16.23.2, 00:00:41, FastEthernet1/1

C    192.168.10.0/24 is directly connected, Serial2/0

     172.172.0.0/32 is subnetted, 1 subnets

D       172.172.172.3 [90/2298856] via 192.168.10.3, 00:00:41, Serial2/0

                      [90/2301416] via 192.168.1.2, 00:00:41, FastEthernet1/0

                      [90/2301416] via 172.16.23.2, 00:00:42, FastEthernet1/1

     172.16.0.0/24 is subnetted, 1 subnets

C       172.16.23.0 is directly connected, FastEthernet1/1

D    192.168.22.0/24 [90/2682856] via 192.168.10.3, 00:00:43, Serial2/0

                     [90/2173416] via 192.168.1.2, 00:00:43, FastEthernet1/0

                     [90/2173416] via 172.16.23.2, 00:00:44, FastEthernet1/1

C    192.168.1.0/24 is directly connected, FastEthernet1/0

[JohnTylerPearce]

Go under R1 and do the following

router eigrp ASN

maximum-paths 1