Tech Library
RSVP – fast reroute
1. Intro Fast reroute can dramatically reduce packet loss in the case a primary path fails. Even if you have a secondary path signaled with the standby feature there is still the possibility of many packet drops. This happens because the message for the failed path must still travel back towards the ingress LSR so […]
RSVP – Secondary Paths
1. Intro In the previous example we tested link coloring with multiple LSPs to the same destination, which is not ideal. In this post we will configure Secondary paths. By default, when network failures occur along the path of RSVP signaled LSPs, traffic will be dropped. The ingress LSR continues to send traffic until a […]
RSVP – Link Coloring
1. Intro Administrative groups provide the ability to mark the interfaces with similar characteristics in a common group. Based on these groups you can restrict the LSPs to use a certain path in the network. Marking the interfaces is known as coloring but is actually based on setting the affinity bits on interfaces. Up to […]
BGP – 6PE
1. Intro We have a small service provider which is providing IPv4 internet services. It has a really simple design with a flat OSPF network, and internal iBGP session via a Route Reflector. No MPLS at this stage. 2. Dual-Stack IPv6 Now, we are being asked to add IPv6 to our network. One way to […]
BGP – RR next hop resolution
1. Intro We have a small service provider with an small MPLS network with a couple of L3VPNs. What matters here is the RR configuration: RR2 will not forward traffic, so we are being asked to remove the LDP configuration. But this will immediately create problems, next hop resolution is no longer working: In the […]
BGP – Inter-AS Option C
1. Intro BGP Option C is the most scalable Inter-AS MPLS L3VPN model. Unlike Options A and B, the PE routers exchange VPN routes directly, while the ASBRs only provide MPLS transport between the autonomous systems. Find next our test topology for this post: Our aim is to have end to end connectivity for Cust-A […]
BGP – Inter-AS Option B
1. Intro BGP Option B is an Inter-AS MPLS L3VPN method in which the ASBRs exchange VPNv4/VPNv6 routes directly using MP-eBGP. It provides better scalability than Option A because the ASBRs do not maintain per-customer VRFs. Find next the our Test Topology : Our aim is to advertise the 192.45.6.1/32 prefix all the way to […]
BGP – Inter-AS Option A
1. Intro BGP Option A is one of the methods for implementing Inter-AS MPLS L3VPNs (VPNs spanning multiple Autonomous Systems). It is the simplest and most isolated of the three common options (A, B, and C). Find next the Test Topology : Our aim is to advertise the 192.45.6.1/32 prefix all the way to R7. […]
BGP – basic multipath
1. Intro BGP typically selects only one best path for each prefix and installs that route in the forwarding table. When BGP multipath is enabled, the device selects multiple equal-cost BGP paths to reach a given destination, and all these paths are installed in the forwarding table. BGP advertises only the active path to its […]
BGP – damping
1. Intro BGP route flapping describes the situation in which BGP systems send an excessive number of update messages to advertise network reachability information. BGP flap damping is a method of reducing the number of update messages sent between BGP peers, thereby reducing the load on these peers, without adversely affecting the route convergence time […]