i am trying to configure two sites with multiple wan link and different link to internet (rough diagram attached). i am trying to setup such that connection between sites and internet remain available till the even when two links are down.
i have setup ospf in all devices and i can connect, traceroute and default route preference is also working fine. OSPF areas are defined as per diagram.
here is what i wanting to achieve
- internet connection for Site B down -> internet traffic from site B need to go through site A and using 2mb wan link if this is not available used 10mb wan link and visa versa (i.e. when site A internet fails it should follow same scenario.
- i want to use both link as much as i can.
note:- interface for 2mb wan connection has the ospf cost of 20 so that this link is not preferred for the traffic.
QOS for voice and video is set on each interface.
I tried using static route with different distance
e.g. ip route 0.0.0.0 0.0.0.0 192.168.1.1
ip route 0.0.0.0 0.0.0.0 192.168.4.4 20
ip route 0.0.0.0 0.0.0.0 192.168. 3.4 40
but this just created loop, doesn't know if interface of other site is down and so forth.
i also looked at PBR but am not able to understand how i can make pbr to failover to other link and making sure PBR also is not creating loop like static routing is creating.
i will appreciate if you guys can give me some idea
only aspect to be checked when introducing 802.1Q header is the MTU: 802.1Q adds 4 bytes to frames
I agree that if the service simply carries ethernet frames it is not a problem 802.1Q tagged frames are still ethernet frames.
>> what if ospf select this link as first choice and send most of the traffic from this link? is there any way of telling not to do that?
with suggested configuration there will be 6 equal cost paths. CEF will perform load balancing based on flows
IP SA exor IP DA exor hash (the hash is a seed that doesn't change until next reload)
So given a flow with a specific IP SA, IP DA a specific link is chosen among the available ones.
A different choice can be made per direction.
per packet load balancing is not recommended
Hope to help
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