Load Balancing BGP, Voice over IP

[tnohsjr]

I currently have implemented two T1 Private Line clear channel IP T's to the Internet, running BGP Protocol. There are two routers which terminate the two T's, and two Cisco 2600's used for loadbalancing the outbound traffic. Behind the two load balancers we have a PIX firewall which is creating our VPN connection to the other location. We are currently trying to get bandwidth of 3mb both outbound and inbound. We are currntly getting load balancing outbound but not inbound. The access routers that our edge routers point two are in two geographically different areas for redundancy, and to make matters even more complicated, we have implemented voice over IP on one of the routers. Only way I know of is to add a third T and have two T's going to one access router, so we can bind the two T's, and leave the third T for redundancy. Do you have any idea how we will be able to get per packet load balancing on the one router and still be able to run voice over IP effectively? I am faced with performance issues, related to the fact that I need the 3mbps full duplex comunication...

[thisisshanky]

You can enable cef

ip cef --- global config mode

int s0

ip load-balance per-packet

int s1

ip load-balance per-packet

This would work in this case, because both T1s are connected between the two 2600s, forming a p-p network.

[tnohsjr]

Will enabling per packet load balancing in this case cause performance issues with voice over IP, due to out of order packet sequence numbers and latency. Obviously the two T's are going to the same access router on my ISP's backbone, but there still the internet in between.

[thisisshanky]

Per packet load balancing with CEF enabled can lead to issues like...reordering of packets. which could lead to issues for VOIP, because VOIP requires in-sequence delivery of the stream.

[thisisshanky]

Since you are already getting outbound LB, and not inbound, you might want to manipulate MED attribute in BGP and advertise your network with equal MED over both the links.

Or you might want to discuss this issue with your ISP, so that ISP would maintain dual static routes with equal metrics for your network, so that inbound LB will happen.