We know that for most of the protocols router does not change anything in the IP header unless we have specifically configured the IP header to be changed for example NAT, QOS markings etc.
In this and few upcoming posts we will specifically look for packet marking when the IP packet gets translated into MPLS labels. We will look into the fact that what exactly happens with the QOS markings when labels are imposed on to the packet.
For internal routing I am using EIGRP in my setup , we can have any routing protocol to achieve the reachability in the network. MPLS uses FIB derived from routing protocols to derive LFIB(Label forwarding information base) which is used for the eventual label switching.
In the above network diag we have three routers running MPLS. Following are the configurations:
mpls label range 100 200 mpls label protocol ldp ! interface Loopback1 ip address 184.108.40.206 255.255.255.255 ! interface FastEthernet1/0 ip address 220.127.116.11 255.255.255.252 mpls ip ! router eigrp 1 network 18.104.22.168 0.0.0.0 network 22.214.171.124 0.0.0.3 auto-summary
mpls label range 300 400 mpls label protocol ldp ! interface Loopback1 ip address 126.96.36.199 255.255.255.255 ! interface FastEthernet1/0 ip address 188.8.131.52 255.255.255.252 mpls ip ! interface FastEthernet1/1 ip address 184.108.40.206 255.255.255.252 mpls ip ! router eigrp 1 network 220.127.116.11 0.0.0.0 network 18.104.22.168 0.0.0.3 network 22.214.171.124 0.0.0.0 no auto-summary
mpls label range 500 600 mpls label protocol ldp ! interface Loopback1 ip address 126.96.36.199 255.255.255.255 ! interface FastEthernet1/0 ip address 188.8.131.52 255.255.255.252 mpls ip ! router eigrp 1 network 184.108.40.206 0.0.0.0 network 220.127.116.11 0.0.0.0 no auto-summary
R1#show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or VC orTunnel Id Switched interface 16 Pop Label 18.104.22.168/30 0 Fa1/0 22.214.171.124 100 Pop Label 126.96.36.199/32 0 Fa1/0 188.8.131.52 101 300 184.108.40.206/32 0 Fa1/0 220.127.116.11
R2#show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or VC or Tunnel Id Switched interface 16 Pop Label 18.104.22.168/8 570 Fa1/0 22.214.171.124 300 Pop Label 126.96.36.199/32 2850 Fa1/1 188.8.131.52
R3#show mpls forwarding-table Local Outgoing Prefix Bytes Label Outgoing Next Hop Label Label or VC or Tunnel Id Switched interface 500 16 184.108.40.206/8 0 Fa1/0 220.127.116.11 501 Pop Label 18.104.22.168/32 0 Fa1/0 22.214.171.124 502 Pop Label 126.96.36.199/30 0 Fa1/0 188.8.131.52
Here we see that mpls is working fine, you can verify the same when you see “label switched ” packet counts increasing in the above command. You can also verify the same with traceroute , it will tell you the imposed label as well as the EXP Bit which I will talk about in my next post.
R1#traceroute 184.108.40.206 Type escape sequence to abort. Tracing the route to 220.127.116.11 1 18.104.22.168 [MPLS: Label 300 Exp 0] 100 msec 12 msec 24 msec 2 22.214.171.124 36 msec 96 msec 96 msec
I will not make this post boring by putting QOS details. Please see my next post for MPLS QOS details…Stay tuned!!
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