Monthly Archives: March 2010

LDP session parameter

There are some timers associated with LDP. The LDP process consist of LDP discovery by which an LDP adjecency will be formed and LDP session (TCP). Note; if there are more than one links between 2 LSRs, there will be … Continue reading

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MPLS TE Notes

Below are some important MPLS-TE notes; MPLS TE- Traffic Engineering In an IP network, routing based only on Destination address. Result in one link being over utilized and another link to under-utilized. We can never do load balancing equally with … Continue reading

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Shared Explicit Style

Assume a tunnel is created between R0 and R5 which are some hops apart. First tunnel is created with BW = 100 and the tunnel is UP. Now if we increase the BW to a higher value such that the … Continue reading

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autoroute announce

R0(config-if)#tunnel mpls traffic-eng autoroute announce This command is to make the head-end LSR to insert IP destinations into the routing table with tunnel interface as next-hop or outgoing interface. <Before this command applied>

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MPLS-TE Basic Config

For MPLS-TE, there are two steps. One: create a tunnel between head end LSR and tail end LSR. Second: Forward traffic via tunnel which now act as virtual link. Here, configuration for tunnel creation is described. Steps to enable MPLS-TE:

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Loop prevention-2: BGP/EIGRP SOO

When the CE-PE routing protocol is OSPF, we used down bit/domain tag to prevent possibility of routing loop. In BGP, when we use a backdoor link in addition to MPLS network, there are possibilities of routing loop. 1) As we … Continue reading

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Loop prevention: Down Bit and Domain Tag

When CE-PE protocol is OSPF, we use “down bit” and “domain tag” to prevent routing loop to occur. When CE-PE protocol is ISIS, we use “up/down” bit for loop prevention. This bit is the higher order bit in the default … Continue reading

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MPLS BGP update Packet

Here is a closer look at the MPLS BGP update packet which carries VPN label, RD and extended communities like BGP cost, RT and Site of Origin attribute (SoO) when MPLS iBGP neighbor is formed, Labelled VPN capability is negotiated … Continue reading

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RR in MPLS

Awesome material about implementing Route Reflector in MPLS network. Functionality of RR in MPLS; It should accept all vpnv4 prefix. RR-groups can be implement so that only those vpnv4 routes filtered by RT/SOO are stored. Reflect all vpnv4 prefix without … Continue reading

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eBGP as CE-PE Routing Protocol in MPLS

We can use any of the below protocols as CE-PR routing protocol in MPLS domain. Connected Static RIPv2 OSPF EIGRP ISIS eBGP Note: we cannot have iBGP session. Advantages of using eBGP as CE_PE routing protocol: 1)NO need to specifically … Continue reading

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