ā01-04-2010 09:11 PM - edited ā03-06-2019 09:09 AM
I have two buildings that are connected together by a multimode fiber. At each building there is a Cisco 1841 router that connects to HQ site via a PTP T1 circuit. Also at each building there is a Cisco 3750 48 port switch for LAN connectivity. I would like to configure a failover configuration, so if one router fails in either building, the building with the failed router can route traffic to the other building. Each building has their own subnet range.
ā01-04-2010 10:26 PM
You would have to configure routing on the switches and either use static routes with different costs, or a routing protocol like OSPF. If you configure routing between HQ and the two sites, and then configure it between the two sites, all traffic destined to the HQ would use the local link. If that link is down, it would traverse the other site.
Is the link between the sites a Layer 2 (switched) link, or routed?
If you post the basic config, I'm sure the community can help you sort out the config that will work. By basic config I mean are you routing or switching what are the VLAN id's on the 3750's.
Dan
ā01-05-2010 12:34 AM
if the connection between the sites L2 then you can
use HSRP as following:
i will assume the following:
each site use one vlan for to reach the router in each building
lets say in building 1 you have the switch operating in L2 only ( no routing)
in building 2 you are using vlan 20
make the L2 link between the sites as trunk that pass vlan 10 and 20
- as long as each site uses its own subnet in this case you need to make the link between the switch and the router inside interface as trunk in the switch
and in the router inside interface you need to create two subinterfaces
lets say building 1
vlan 10
network 10.1.1.0/24
building 2
vlan 20
network 20.1.1.0/24
as mentioned above vlan 10 and 20 have to be created in both switches
and trunked between them as well ( i wish the inter sites link is L2)
site 1 router
int fa0/0.1
encapsulation dot1q vlan 10
ip add 10.1.1.1 255.255.255.0
standby 1 ip 10.1.1.100
standby 1 preempt
standby 1 priority 110
standby track int [ousideinterface going to the HQ]
int fa0/0.2
encapsulation dot1q vlan 20
ip add 20.1.1.2 255.255.255.0
standby 2 ip 20.1.1.100
standby 2 preempt
standby 2 priority 100
site 2 router
int fa0/0.1
encapsulation dot1q vlan 10
ip add 10.1.1.2 255.255.255.0
standby 1 ip 10.1.1.100
standby 1 preempt
standby 1 priority 100
int fa0/0.2
encapsulation dot1q vlan 20
ip add 20.1.1.1 255.255.255.0
standby 2 ip 20.1.1.100
standby 2 preempt
standby 2 priority 110
standby 2 track int [ouside interface going to the HQ]
in this case site 1 default gateway will be 10.1.1.100 and the primary exit will be the router in building 1 if this router fail or the link to the HQ goes down the router in building 2 will take over same concept for building 2
this is based on the assumption that the link between the two buildings is L2
if not the above solution is not valid
if link between the buildings is L3 router link in this case you need to consider routing and as mentioned in the previous post you will need to enable routing in the switches to have a redundant path to the HQ
you can use any routing protocol but this depends on what routing you use between each site and the HQ site
good luck
if helpful Rate
ā01-05-2010 06:16 AM
You are correct to assume on the way the two buildings are configured. I will test your config and let u know how it goes. Thank you.
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