Sometimes you notice a network design where you have more than one serial link between two routers. A single serial link doesn’t provide enough bandwidth or maybe in case you want some extra redundancy. All the interfaces on a router need a different IP address, a design that looks like this:





Multilink PPP allows us to make a combination of multiple physical serial links into a single logical link or MLP bundle. MLP is used to aggregate multiple WAN links into one logical channel for the transportation of traffic from one router to another, MLP enable the load—balancing of traffic from different links as we and allows some level of redundancy in case of line failure on a single link.MLP Supports a maximum of ten member links per bundle or single logical link.





lets take a look of its configuration:





Multilink point-to-point protocol configuration :-





Topology:









Goal:

configure the topology as per the diagram, we are using serial range 3/0 to 3/5.

configure single logical link, group number 1

configure channel ip address 192.168.1.0/24

Configure EIGRP 65100 to reach fastethernet 10.1.1.1, 20.1.1.1





R1(config)#interface multilink 1



R1(config-if)#ppp multilink group 1 R1(config-if)#ip address 192.168.1.1 255.255.255.0 R1(config-if)#exit

R1(config)#interface serial 3/0 R1(config-if)#no ip address R1(config-if)#encapsulation ppp R1(config-if)#ppp multilink R1(config-if)#ppp multilink group 1 R1(config-if)#no shutdown R1(config-if)#exit

R1(config)#interface serial 3/1 R1(config-if)#no ip address R1(config-if)#encapsulation ppp R1(config-if)#ppp multilink group 1 R1(config-if)#no shutdown R1(config-if)#exit R1(config)#

R1(config)#interface serial 3/2 R1(config-if)#no ip address R1(config-if)#encapsulation ppp R1(config-if)#ppp multilink group 1 R1(config-if)#no shutdown R1(config-if)#exit

R1(config)#interface serial 3/3 R1(config-if)#no ip address R1(config-if)#encapsulation ppp R1(config-if)#ppp multilink group 1 R1(config-if)#no shutdown R1(config-if)#exit

R1(config)#interface serial 3/4 R1(config-if)#no ip address R1(config-if)#encapsulation ppp R1(config-if)#ppp multilink group 1 R1(config-if)#no shutdown R1(config-if)#exit

R1(config)#interface serial 3/5 R1(config-if)#no ip address R1(config-if)#encapsulation ppp R1(config-if)#ppp multilink group 1 R1(config-if)#no shutdown R1(config-if)#exit





R2(config)#interface multilink 1 R2(config-if)#ppp multilink group 1 R2(config-if)#ip address 192.168.1.2 255.255.255.0 R2(config-if)#no shutdown R2(config-if)#exit

R2(config)#interface serial 3/5 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# exit

R2(config)#interface serial 3/4 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# exit

R2(config)#interface serial 3/3 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# exit

R2(config)#interface serial 3/3 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# exit

R2(config)#interface serial 3/2 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# no ip address R2(config-if)# exit

R2(config)#interface serial 3/1 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# exit

R2(config)#interface serial 3/0 R2(config-if)# no ip address R2(config-if)# encapsulation ppp R2(config-if)# ppp multilink group 1 R2(config-if)# no shutdown R2(config-if)# no ip address R2(config-if)# exit



R1#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 10.1.1.1 YES manual up up Serial3/0 unassigned YES unset up up Serial3/1 unassigned YES unset up up Serial3/2 unassigned YES unset up up Serial3/3 unassigned YES unset up up Serial3/4 unassigned YES unset up up Serial3/5 unassigned YES unset up up Multilink1 192.168.1.1 YES manual up up







R2#show ip interface brief Interface IP-Address OK? Method Status Protocol FastEthernet0/0 20.1.1.1 YES manual up up Serial3/0 unassigned YES unset up up Serial3/1 unassigned YES unset up up Serial3/2 unassigned YES unset up up Serial3/3 unassigned YES unset up up Serial3/4 unassigned YES unset up up Serial3/5 unassigned YES unset up up Multilink1 192.168.1.2 YES manual up up





R1(config)#router eigrp 65100 R1(config-router)#network 10.0.0.0 R1(config-router)#network 192.168.1.0 R1(config-router)#no auto-summary R1(config-router)#exit





R2(config)#router eigrp 65100 R2(config-router)#network 20.0.0.0 R2(config-router)#network 192.168.1.0 R2(config-router)#no auto-summary R2(config-router)#exit





R1#show run interface multilink 1 Building configuration...

Current configuration : 104 bytes ! interface Multilink1 ip address 192.168.1.1 255.255.255.0 ppp multilink ppp multilink group 1 end





R2#show run interface multilink 1 Building configuration...

Current configuration : 104 bytes ! interface Multilink1 ip address 192.168.1.2 255.255.255.0 ppp multilink ppp multilink group 1 end





R1#show interfaces multilink 1 Multilink1 is up, line protocol is up Hardware is multilink group interface Internet address is 192.168.1.1/2 4 MTU 1500 bytes, BW 9264 Kbit/sec, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, LCP Open, multilink Open





R2#show interfaces multilink 1 Multilink1 is up, line protocol is up Hardware is multilink group interface Internet address is 192.168.1.2/24 MTU 1500 bytes, BW 9264 Kbit/sec, DLY 20000 usec, reliability 255/255, txload 1/255, rxload 1/255 Encapsulation PPP, LCP Open, multilink Open





R1#show interfaces multilink 1 | include line protocol Multilink1 is up, line protocol is up





R2#show interfaces multilink 1 | include line protocol Multilink1 is up, line protocol is up





R1#show ppp multilink

Multilink1 Bundle name: R2 Remote Endpoint Discriminator: [1] R2 Local Endpoint Discriminator: [1] R1 Bundle up for 00:31:18, total bandwidth 9264, load 1/255 Receive buffer limit 72000 bytes, frag timeout 1000 ms 0/0 fragments/bytes in reassembly list 0 lost fragments, 93 reordered 0/0 discarded fragments/bytes, 0 lost received 0xEA received sequence, 0xF0 sent sequence Member links: 6 active , 0 inactive (max 255, min not set) Se3/5, since 00:31:18 Se3/4, since 00:30:51 Se3/3, since 00:30:25 Se3/2, since 00:29:29 Se3/1, since 00:28:55 Se3/0, since 00:28:27





R2#show ppp multilink

Multilink1 Bundle name: R1 Remote Endpoint Discriminator: [1] R1 Local Endpoint Discriminator: [1] R2 Bundle up for 00:31:54, total bandwidth 9264, load 1/255 Receive buffer limit 72000 bytes, frag timeout 1000 ms 0/0 fragments/bytes in reassembly list 0 lost fragments, 97 reordered 0/0 discarded fragments/bytes, 0 lost received 0xFC received sequence, 0xF5 sent sequence Member links: 6 active , 0 inactive (max 255, min not set) Se3/5, since 00:31:54 Se3/4, since 00:31:27 Se3/3, since 00:31:00 Se3/2, since 00:30:04 Se3/1, since 00:29:31 Se3/0, since 00:29:02





R1#traceroute 20.1.1.1 Type escape sequence to abort. Tracing the route to 20.1.1.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.1.2 92 msec 40 msec 20 msec





R2#traceroute 10.1.1.1 Type escape sequence to abort. Tracing the route to 10.1.1.1 VRF info: (vrf in name/id, vrf out name/id) 1 192.168.1.1 20 msec 16 msec 20 msec







