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New Member

Design question

Hello

I have a design question. I have two 5505 with RSM in each that are connected to each other with 200Mb trunk. Right now RSM of the first switch is in VLAN 1; RSM of the second switch is in the VLAN 2.

Altogether I have about 20 VLANs. I am planning to run HSRP between both RSMs for redundancy. What would be the best way of doing it?

Here is what I think needs to happen:

1.Change the IP address of the second RSM and make it a part of VLAN 1

2.Reconfigure all VLAN

3.For even-numbered VLANs make the primary gateway RSM1

4.For odd-numbered VLANs make the primary gateway RSM 2

5.Copy the configuration for VLANs from RSM 1 to RSM2

I do not have much experience in design so any input is more than welcome.

Thanks,

6 REPLIES
New Member

Re: Design question

To correctly do HSRP your routers should be setup so they are virtually identically. The only differences between them should be the vlan ip addresses and the hsrp differences such as priority levels. That way if one rsm fails the other will have the same routing tables eg static routes and can pass traffic.

1. The RSM's will be a member of all vlans, create vlan 1 on the 2nd rsm and give it an ip address in the same range.

2. add hsrp statements to all vlans, preempt, priority etc. Make sure you put them in separate hsrp groups eg for vlan 1 use "standby 1 ip ..."

for vlan 2 use " standby 2.."

make these match on each rsm

3. you can do it this way but you should ensure that layer 3 matches layer 2 ie the root of the spanning tree for vlan 1 is on the same 5505 as the switch that will be the active router in the hsrp.

you should ensure you are running similar software (identical is better as there are a few bugs around with hsrp)

with all the above you should be able to distribute hsrp to your network. I advise doing this on a vlan by vlan basis, there will be some loss of data whilst the routers negotiate active/standby states so I would do it at an out of hourse date. After that using "show standby brief" will give you a brief indication of hsrp states. hope that has helped.

New Member

Re: Design question

Would this work?

RSM 1:

interface vlan 1

ip address 172.17.1.2 255.255.0.0

standby 100 ip 172.17.1.3 (ip address of vlan 1 on RSM2?)

standby 100 priority 100

standby prempt

________________________

RSM 2

interface vlan 1

ip address 172.17.1.3 255.255.0.0

standby 100 ip 172.17.1.2 (ip address of vlan 1 on RSM1?)

standby 100 priority 100

standby prempt

Is this correct? Do I need anything else for HSRP to function correctly?

New Member

Re: Design question

looks ok but whichever 5500 is the root bridge for vlan 1, it's hsrp standby priority should be higher so that the root bridge has the active HSRP process.

best regards,

Carl

New Member

Re: Design question

1. How do I find out which one is the root bridge?

2. Standby ip address is that an address for the RSM module of the other 5505 or is it a virtual ip address and both RSM should point to it?

Thanks a lot,

New Member

Re: Design question

show spantree 1 for vlan 1 etc

you'll find the root by looking at

"Designated Root Cost" that will point you to the root of the spanning tree for that vlan, it will be "1/0"on the root, also the designated root mac address and the bridge mac will be the same.

I also think you are not doing HSRP correctly, the standby ip addresses on each RSM in vlan 1 shoulg be the same. It is that IP Address that the clients point to. You will have two routers trying to become the default gateway for the vlan 1, as both have the same priority, the one (I think) with the higher ip address will be chosen as the designated router. the config should be

RSM1

int vlan 1

ip address 172.17.1.2 255.255.0.0

standby 100 ip 172.17.1.x

standby 100 priority 200

standby 100 preempt

RSM1

int vlan 1

ip address 172.17.1.3 255.255.0.0

standby 100 ip 172.17.1.x

standby 100 priority 100

standby 100 preempt

that way the RSM1 will be the Active Router. Choose x to be the ip address that you designate to the clients. You can also have multiple groups within the vlan and have half clients on one router standby address and half on the other but hsrp should be ok as above. hope this helps

New Member

Re: Design question

Thanks a lot fot you help,

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