MPLS Network Configuration on GNS3

What is MPLS (Multi-Protocol Label Switching) ?

MPLS is lable base fast switching, MPLS is a technique which forward the packets in network on bases of labels.

Why MPLS?

Router use the process switching in which whenever router received a packet it checks its IP address match with routing table and forward packet, send ARP request for MAC addres. This Process become a little slow when router dealing with a lot of IP packets, in case of VOIP e.g. a IP-Phone call may using 50packets/second then router have to perform process switching for every packets  

But in MPLS instead of processing above large packet each time route just use a label to forward a packet which saving some processing cycle and made fast forwarding.

MPLS Configuration on GNS3:

Design above lab in gns3 and configure IP address and EIGRP according to EIGRP configuration on GNS3 . In our lab R3 is provider router where as R2, R4 and R5 are the provider edge routers.

On Cisco router to enable the MPLS you required to :

1. Enable CEF(cisco express forwarding) on router
2. Change MTU (maximum transmission unit) from 1500 to 1512 on MPLS enabled interfaces, becase MPLS header is of 4 bytes and one interface have maximum of three.

R2 MPLS configuration Commmands:

R2#conf t
R2(config)#ip cef
R2(config)#int s1/1
R2(config-if)#mpls label protocol ldp
R2(config-if)# mpls ip
R2(config-if)# mpls mtu 1512
R2(config-if)#ip route-cache cef

R3 MPLS configuration Commmands:

R3(config)#ip cef
R3(config)#int s1/1
R3(config-if)#ip route-cache cef
R3(config-if)#mpls mtu 1512
R3(config-if)#mpls ip
R3(config-if)#mpls label protocol ldp

R3(config-if)#int s1/2
R3(config-if)#mpls mtu 1512
R3(config-if)#ip route-cache cef
R3(config-if)#mpls ip
R3(config-if)#mpls label protocol ldp

R3(config)#int s1/0

R3(config-if)#mpls mtu 1512
R3(config-if)#ip route-cache cef
R3(config-if)#mpls ip
R3(config-if)#mpls label protocol ldp

R4 MPLS configuration Commmands:

R4(config)#ip cef
R4(config)#int s1/0
R4(config-if)# mpls ip

R4(config-if)#mpls label protocol ldp
R4(config-if)# mpls mtu 1512

R5 MPLS configuration Commmands:

R5(config)#ip cef
R5(config)#int s1/0
R5(config-if)# mpls label protocol ldp
R5(config-if)# mpls ip
R5(config-if)# mpls mtu 1512
R5(config-if)#
R5(config-if)#ip route-cache cef

MPLS Verification Commands:

R3#show mpls ldp neighbor


R3#show mpls forwarding-table


R3#show ip cef



R3#sh mpls ip binding




R3#sh mpls forwarding-table interface serial 1/1