asked on

Cisco IOS - Provide a secondary/backup route to a specific subnet

How do I setup routes to allow for a secondary route to become active in the event of an issue with a primary route ?

I have two sites, each with two IOS routers.

R1 and R2 are a HSRP pair in the primary site, and R3 and R4 are a HSRP pair in a satellite site.

There is a private link between R1 and R3, and a second private link between R2 and R4.

The attached document shows the current configuration. I want the following two subnets to communicate with each other.

192.168.10.0/24 - on R1 and R2
192.168.12.0/24 - on R3 and R4

These subnets should communicate over the primary link between R1 and R3 under normal circumstances. If that link fails then the traffic between the subnets needs to move to the link between R2 and R4.

Will the ip route entries on each router, as shown in the attached document, produce the desired affect ?

If not, what is the preferred/recommended way to achieve this ?

TIA Redundant-Routing-Configuration.pdf

Sanjeevloke

static seems fine ..
what type of links are those serial or ethernet ?
if ethernet just static wont switchover to second route for that u have to configure IP SLA with track of static route..

Sanjeevloke

if links are ethernet buy HSRP tracking u can just do failover no need of all static routes ..
every router will have just one default route to WAN.

in HSRP u have to track WAN IP with IP SLA so that prorirty of failed WAN link router reduces and
passive router become active and traffic flows through it ..

ccfcfc

ASKER

Sanjeevloke,

Thanks for the replies.

The links are ethernet, which would explain why nothing happens when the link drops based on your first response.

I'm trying to avoid the whole router failing over.

The links between the sites occasionally go down but there has been no need to failover between the routers for over two years, so I would prefer that the route changes to use the alternate link when necessary rather than switching the whole router.

Can you point me to any documentation that details the IP SLA process, as I haven't used this before ?

Sanjeevloke

ok sure....

Sanjeevloke

ip sla monitor 10
type echo protocol ipIcmpEcho 172.29.139.134 source-ipaddr 172.29.139.132 --------Remote WAN ip
frequency 300
ip sla monitor schedule 10 start-time now life forever

track 1 rtr 10 reachability

ip route 0.0.0.0 0.0.0.0 1.1.1.1 track 10 ---------Primary route

mikebernhardt

It would be a lot easier to just use a dynamic routing protocol like EIGRP to manage this. Just configure it on all 4 routers and they will take care of the whole thing. Messing with IP SLA and HSRP seems like a more complicated configuration to avoid dynamic routing.

The very simplest way to do it would be on all 4 routers to just add the following:
router eigrp 1
network 192.168.0.0 255.255.0.0
no auto-summary

that's it!

Steve Jennings

Agree with mikebernhardt. If possible use EIGRP.

Steve

ccfcfc

ASKER

If I implement EIGRP will I need to remove the HSRP elements of my config ?

mikebernhardt

They have nothing to do with each other and they can co-exist. But if the only purpose of the HSRP is to have a single next-hop address for your static routes, then you can remove it. You will have to remove the static routes once EIGRP is configured though.

ccfcfc

ASKER

So, if I do the following.....

1. Setup EIGRP and include all networks present across all four routers.
2. Remove any HSRP entries.

This will give me resilience if any router fails, or any interface or link to any router fails.

Is that correct ?

mikebernhardt

Yes, but are you using HSRP for any LAN operations or only for your routing? Don't remove the HSRP if it's also giving you a resilient default gateway on LANs. that is completely independent of routing.

ccfcfc

ASKER

Yes, HSRP is giving me resilient default gateways. Apologies if I didn't make that clear.

Apologies also for the dumb questions. I haven't used EIGRP before so I'm on a steep learning curve.

Sanjeevloke

I agree with running EIGRP/OSPF between sites is a better solution..
But if someone is new it will be difficult for troubleshooting when issue appears ...

Steve Jennings

No, just get familiar with what the routing table looks like when everything is normal. Once you have it installed and running, break some things and take note of what hsppens.

Steve

SOLUTION

ipajones

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Sanjeevloke

His links are Ethernet so i dont think ....track of interface will work without IP SLA ..
If links were serial no issues ...

ipajones

@sanjeevloke: Why not ? You can track the ethernet interfaces just like a serial interface, when the link drops the interface will go down.

Sanjeevloke

no ethernet interface wont go down as its protocol stays up only ..

SOLUTION

mikebernhardt

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mikebernhardt

For the author's benefit: The way EIGRP works in a nutshell is that 2 routers become "neighbors" and exchange information about routes. The router uses the best path to the remote site, which in your case would normally be the connected WAN link. If that link is bad for any reason, the 2 routers can't talk, so those routes drop. At each site, the 2 routers there would communicate across the LANs to each other, again sharing their all of routing information. So the router with the bad WAN link will simply take the next-best route through its partner router and across the other WAN link.

Easy, huh?

ccfcfc

ASKER

So, based on the responses to my initial question and the network diagram that I have attached, would the following router configurations be correct to ensure that -

1. My routers will failover under HSRP in the event of interface issues and the default gateway addresses for connected devices will remain the same.
2. Traffic will be routed over the private links between the sites using the preferred link under normal circumstances and the second link if there are issues with the preferred link.

Router 1

interface Vlan100
ip address 192.168.10.1 255.255.255.0
standby 10 ip 192.168.10.254
standby 10 priority 150
standby 10 preempt
standby 10 track GigabitEthernet0/0 60
interface Vlan200
ip address 192.168.11.1 255.255.255.0
standby 20 ip 192.168.11.254
standby 20 priority 150
standby 20 preempt
standby 20 track GigabitEthernet0/0 60
router eigrp 1
network 192.168.10.0 255.255.0.0
network 192.168.11.0 255.255.0.0
network 192.168.12.0 255.255.0.0
network 192.168.20.0 255.255.0.0
no auto-summary

Router 2

interface Vlan100
ip address 192.168.10.2 255.255.255.0
standby 10 ip 192.168.10.254
standby 10 preempt
standby 10 track GigabitEthernet0/0
interface Vlan200
ip address 192.168.11.2 255.255.255.0
standby 20 ip 192.168.11.254
standby 20 preempt
standby 20 track GigabitEthernet0/0
router eigrp 1
network 192.168.10.0 255.255.0.0
network 192.168.11.0 255.255.0.0
network 192.168.12.0 255.255.0.0
network 192.168.20.0 255.255.0.0
no auto-summary

Router 3

interface GigabitEthernet0/0.1
ip address 192.168.13.1 255.255.255.0
standby 10 ip 192.168.13.254
standby 10 priority 150
standby 10 preempt
standby 10 track GigabitEthernet0/1
router eigrp 1
network 192.168.10.0 255.255.0.0
network 192.168.11.0 255.255.0.0
network 192.168.12.0 255.255.0.0
network 192.168.20.0 255.255.0.0
no auto-summary

Router 4

interface GigabitEthernet0/0
ip address 192.168.13.2 255.255.255.0
standby 10 ip 192.168.13.254
standby 10 priority 90
standby 10 preempt
standby 10 track GigabitEthernet0/1
router eigrp 1
network 192.168.10.0 255.255.0.0
network 192.168.11.0 255.255.0.0
network 192.168.12.0 255.255.0.0
network 192.168.20.0 255.255.0.0
no auto-summary

SOLUTION

ipajones

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ASKER CERTIFIED SOLUTION

mikebernhardt

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mikebernhardt

Have I answered your question satisfactorily? If we're done, you should accept an answer so that the question will be closed.

ipajones

...or answers ! :)

ccfcfc

ASKER

I'm waiting for an opportunity to arrange a maintenance window so that I can make and test the config changes.

It may not be quick as they take some time to schedule on this system.

mikebernhardt

Got it, no problem. Just making sure you didn't abandon the question.

ccfcfc

ASKER

Quick update.

I'm still waiting for a maintenance window to be arranged so that I can implement and test the changes.

ipajones

In my view a working solution was provided and the points should be split between @mikebernhardt and @ipajones.

Thank you.
--IJ

mikebernhardt

Agree with ipajones.

digitap

I've requested that this question be deleted for the following reason:

Not enough information to confirm an answer.

mikebernhardt

The question was abandoned some time ago and both of us experts agreed that the points should be split between us. We have him thorough answers and he promised to try them then never returned. Points should be awarded.

ipajones

I agree with @mikebernhardt in that a working solution was provided and that the points should be split between @mikebernhardt and @ipajones for the answers we provided. Please clarify why you say not enough information was provided ?

Thanks
--IJ

ipajones

In my opinion the comments (http:#36961337 and http:#36978825) complimented and clarified some points regarding the initial solution provided by @mikebernhardt (http:#36963085). Comment http:#36981103 by @mikebernhardt also provided more details and clarification.

The answers and details provided enough information to enable the asker to setup EIGRP to provide backup routes (Feasible successors) given the topology provided.

Some guidance with regard to HSRP and directly tracking an interface within the HSRP config was also provided and this included a discussion as whether HSRP was definitely required.

--IJ

mikebernhardt

Having just looked through this thread again, I'm going to go with ipajones explanation or which comments were most helpful. If I was to grade the answers, I would accept my answer http:#36981103 with a strong assist by ipajones 2 answers http:#36961337 and http:#36978825. I have no problem with splitting points evenly between us.

The question was essentially about how to provide a resilient backup solution. We suggested dynamic routing and also differentiated and clarified the proper use of HSRP and IP SLA vs. routing in order to deal with various failure scenarios.

mikebernhardt

I don't see the points awarded...