EIGRP & HSRP

[aspry]

Can you please help.

Our satellite office is to be split into 4 subnets.

We have a frame-relay network and are suing EIGRP, and are looking to load share using EIGRP.

2 routers at the satellite connecting to 3 routers at the head office over 4 pvcs.

We intend to route 2 subnets down each router. i.e. 2 subnets down r1 to r3 and r4 and 2 subnets down r2 to r4 and r5.

Using HSRP we will have 2 groups so that 2 subnets are active on one router and passive on the other and vice versa.

What I want to know is will the routing tables in r1 and r2 advertise just the active subnets that it is routing or because it knows of all 4 subnets will it advertise all 4 of them.

Hope this make sense.

Any pointers to documentation much appreciated.

[globalnettech]

Hello,

basically, EIGRP will advertise whatever interface you specify with the 'network' statement, provided the interface is up/up.

From what you are saying, you have r1 and r2 at the satellite location, and r3, r4, and r5 at the head office location ?

If that is correct, your configuration could look like this:

hostname r1

!

interface ethernet 0

ip address 192.168.1.3 255.255.255.0

standby 1 ip 192.168.1.1

standby 1 priority 110

standby 1 preempt

standby 2 ip 192.168.1.2

standby 2 preempt

!

hostname r2

!

interface ethernet 0

ip address 192.168.1.4 255.0.0.0

standby 1 ip 192.168.1.1

standby 1 preempt

standby 2 ip 192.168.1.2

standby 2 priority 110

standby 2 preempt

Now, if you give half of your hosts at the satellite connection the IP address of standby group 1 as their default gateway, and the other half of your hosts the IP address of standby group 2, you will have a fault-tolerant load balancing configuration.

Have a look at the document below as well. If possible, can you post the full configurations of your routers ?

Using HSRP for Fault-Tolerant IP Routing

http://www.cisco.com/en/US/tech/tk1330/technologies_design_guide_chapter09186a008066670b.html

HTH,

GNT

[aspry]

Thank you for your reply.

I can see how we could use the configurations you have included.

Unfortunately, behind each router there are switches and we need these in different vlans, due to some legacy stuff, also the PCs in the satellite office use dhcp.

Just looking whether responses from the server in the head office will be routed back to the satellite office correctly bu just using the routing tables forwarded by the satellite office.

[Richard Burts]

Andrew

There is not an impact on what EIGRP will advertise from running HSRP. EIGRP will advertise subnets based on the network statements that are specified and has no consideration for whether HSRP is leader or standby.

You do raise a valid point that HSRP will help steer traffic to R1 or R2 to be forwarded to Head Office. But routing traffic from HO to the Satellite Office will not be affected by HSRP. So you need something to modify routing at HO. I would suggest offset lists on R1 and R2. Your config might look something like this:

hostname R1

interface fastethernet 0/0.32

ip address 172.18.32.2 255.255.224.0

standby 1 ip 172.18.32.1

standby 1 priority 105

standby 1 preempt

interface fastethernet 0/0.64

ip address 172.18.64.2 255.255.224.0

standby 2 ip 172.18.64.1

standby 2 priority 105

standby 2 preempt

interface fastethernet 0/0.96

ip address 172.18.96.2 255.255.224.0

standby 3 ip 172.18.96.1

standby 3 priority 101

standby 3 preempt

interface fastethernet 0/0.128

ip address 172.18.128.2 255.255.224.0

standby 4 ip 172.18.128.1

standby 4 priority 101

standby 4 preempt

!

router eigrp 100

network 172.18.32.0 0.0.31.255

network 172.18.64.0 0.0.31.255

network 172.18.96.0 0.0.31.255

network 172.18.128.0 0.0.31.255

offset-list 10 out 1000

access-list 10 permit 172.18.96.0

access-list 10 permit 172.18.128.0

!

hostname R2

interface fastethernet 0/0.32

ip address 172.18.32.3 255.255.224.0

standby 1 ip 172.18.32.1

standby 1 priority 101

standby 1 preempt

interface fastethernet 0/0.64

ip address 172.18.64.3 255.255.224.0

standby 2 ip 172.18.64.1

standby 2 priority 101

standby 2 preempt

interface fastethernet 0/0.96

ip address 172.18.96.3 255.255.224.0

standby 3 ip 172.18.96.1

standby 3 priority 105

standby 3 preempt

interface fastethernet 0/0.128

ip address 172.18.128.3 255.255.224.0

standby 4 ip 172.18.128.1

standby 4 priority 105

standby 4 preempt

!

router eigrp 100

network 172.18.32.0 0.0.31.255

network 172.18.64.0 0.0.31.255

network 172.18.96.0 0.0.31.255

network 172.18.128.0 0.0.31.255

offset-list 10 out 1000

access-list 10 permit 172.18.32.0

access-list 10 permit 172.18.64.0

HTH

Rick

[aspry]

Thank you for the reply and advice, much appreciated.

Andy