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Print This PostWhen it comes time to upgrade a single T1 that is running at capacity, it is easy to add additional T1 circuits by using Multilink PPP. If the original T1 is a point to point circuit, first you must make sure it is running the Point to Point protocol, as apposed to HDLC. This is easy enough to do by using the command encapsulation ppp command on the serial interface of each router. Once this is done, a second circuit is easy to add by creating a Multilink interface.
interface Multilink1 description Telco CKT: DS1NT-99999 ip address 1.1.1.1 255.255.255.252 ppp multilink ppp multilink fragment disable ppp multilink links minimum 1 ppp multilink group 1
As you can see, the layer 3 configuration now goes on the Multilink interface, along with the number/identifier of the multilink group. The ppp multilink links minimum command, the Network Control Protocols for an MLP bundle are disabled until the bundle has the minimum number of configured links. By default, packet fragmentation is enabled on the multilink interface, you can disable this behavior if fragmentation causes performance degradation.
The serial interfaces that are participating in the group now just have the ppp encapsulation and group membership configured.
interface Serial0/0/0:0 description Telco CKT: DS1NT-99999 / LEC: ABCDE no ip address encapsulation ppp ppp multilink ppp multilink group 1 ! interface Serial0/0/1:0 description Telco CKT: DS1NT-99999 / LEC: ABCDE no ip address encapsulation ppp ppp multilink ppp multilink group 1
The following is an entire serial configuration with two dual port serial wics install into a 2800 series router.
card type t1 0 0 card type t1 0 1 ! controller T1 0/0/0 framing esf linecode b8zs channel-group 0 timeslots 1-24 description Telco CKT: DS1NT-99999 / LEC: ABCDE ! controller T1 0/0/1 framing esf linecode b8zs channel-group 0 timeslots 1-24 description Telco CKT: DS1NT-99999 / LEC: ABCDE ! controller T1 0/1/0 framing esf linecode b8zs channel-group 0 timeslots 1-24 description Telco CKT: DS1NT-99999 / LEC: ABCDE ! controller T1 0/1/1 framing esf linecode b8zs channel-group 0 timeslots 1-24 description Telco CKT: DS1NT-99999 / LEC: ABCDE ! interface Multilink1 description Telco CKT: DS1NT-99999 ip address 1.1.1.1 255.255.255.252 ppp multilink ppp multilink fragment disable ppp multilink links minimum 1 ppp multilink group 1 ! interface Serial0/0/0:0 description Telco CKT: DS1NT-99999 / LEC: ABCDE no ip address encapsulation ppp ppp multilink ppp multilink group 1 ! interface Serial0/0/1:0 description Telco CKT: DS1NT-99999 / LEC: ABCDE no ip address encapsulation ppp ppp multilink ppp multilink group 1 ! interface Serial0/1/0:0 description Telco CKT: DS1NT-99999 / LEC: ABCDE no ip address encapsulation ppp ppp multilink ppp multilink group 1 ! interface Serial0/1/1:0 description Telco CKT: DS1NT-99999 / LEC: ABCDE no ip address encapsulation ppp ppp multilink ppp multilink group 1
Author Info:
Scott is the Founder, Administrator, Architect, Chief Editor and Shameless Hack who wrote and runs Xpresslearn.Scott has been working in the networking field for 13 years and has experience in all the areas: Lan, Wan, Security, Optimization, High Availability, Wireless, and others.
When he is not working on further development of Xpresslearn, Scott loves spending time with his family and has such hobbies as Camping, Fishing, Cars, and Woodworking.