A system for improving network performance when communicating between a first site network and a second site network via an Internet Protocol, IP, based transport network, wherein: the first and second site networks include a local area network, LAN, and a plurality of host/media gateways, MGWs, connected to the LAN, wherein the LAN includes a plurality of IP subnets for connecting different host/MGWs, and the host/MGWs on each IP subnet form a different host group; first and second Site Edge Routers, SERs, (31, 32) in each site network handle traffic from different host/MGWs, wherein all of the host/MGWs in a host group are configured to use the same SER as a default router, said SERs being connected to the LAN as a redundant backup pair in which each SER in a pair backs up the other SER in the pair; the first SER connects to a first Provider Edge, PE, router (PE_A) in the transport network via a first SER-PE link; the second SER connects to a second PE router (PE_B) via a second SER-PE link; each of the SER-PE links has enough spare capacity to carry traffic coming from both the first and second SERs in case the first or second SER fails; and means within the first and second SERs for providing preferred routing information to the first and second PE routers, thereby guaranteeing symmetric paths for bidirectional traffic wherein each given SER advertises with a first Border Gateway Protocol Multi-Exit Discriminator, BGP MED, having a low value, a routing prefix for the host group served by the given SER, and advertises with a second BGP MED having a higher value than the first BGP MED, the routing prefix for the host group served by the SER that the given SER backs up. the first and second site networks include a local area network, LAN, and a plurality of host/media gateways, MGWs, connected to the LAN, wherein the LAN includes a plurality of IP subnets for connecting different host/MGWs, and the host/MGWs on each IP subnet form a different host group; first and second Site Edge Routers, SERs, (31, 32) in each site network handle traffic from different host/MGWs, wherein all of the host/MGWs in a host group are configured to use the same SER as a default router, said SERs being connected to the LAN as a redundant backup pair in which each SER in a pair backs up the other SER in the pair; the first SER connects to a first Provider Edge, PE, router (PE_A) in the transport network via a first SER-PE link; the second SER connects to a second PE router (PE_B) via a second SER-PE link; each of the SER-PE links has enough spare capacity to carry traffic coming from both the first and second SERs in case the first or second SER fails; and means within the first and second SERs for providing preferred routing information to the first and second PE routers, thereby guaranteeing symmetric paths for bidirectional traffic wherein each given SER advertises with a first Border Gateway Protocol Multi-Exit Discriminator, BGP MED, having a low value, a routing prefix for the host group served by the given SER, and advertises with a second BGP MED having a higher value than the first BGP MED, the routing prefix for the host group served by the SER that the given SER backs up.