Cisco – Combing T1 interfaces to increase speed

Recently I was working on a project that had a very remote office that could not get high speed connections to its location. So, they wanted to combine 4 T1s that were already in the building to boost throughput. I had done this exact thing with many different ISPs but never Verizon/MCI . They do things just a bit different, so this entry is about what is needed to combine these links on Verizon’s network.

The key here is to use a Multilink Frame relay interface. This is a Virtual interface that will combine the individual interfaces. Its very similar to a BVI in concept. As Cisco says it: The Multilink Frame Relay feature enables you to create a virtual interface called a bundle or bundle interface. The bundle interface serves as the Frame Relay data link and performs the same functions as a physical interface. 

At the bottom of this entry all the parts of the config are listed

First we needed to create the MFR interface itself. The number is up to you, I created 34 – feel free to change that.

interface MFR34
mtu 4470 — MTU Verizon said to set
no ip address
no ip redirects
encapsulation frame-relay IETF – Encapsulation used.
frame-relay multilink bid u11111-11
frame-relay lmi-type ansi
!

Next we need to create the sub interface , which will be used as our DLCI and our L3 interface.
interface MFR34.500 point-to-point
description multilink:MLFR:3xT1
bandwidth 6000
ip address x.x.x.x x.x.x.x
ip nat outside
snmp trap link-status
no cdp enable
no arp frame-relay
frame-relay interface-dlci 500 IETF
!

Then we will bond the interface to our MFR interface.

interface Serial0/0/0:0
mtu 4470
bandwidth 1536
no ip address
 encapsulation frame-relay MFR34
load-interval 30
cdp enable
no arp frame-relay
!

The T1 and MFR config are below:

controller T1 0/0/0
cablelength long 0db
channel-group 0 timeslots 1-24
!
controller T1 0/0/1
cablelength long 0db
channel-group 0 timeslots 1-24
!
controller T1 0/0/2
cablelength long 0db
channel-group 0 timeslots 1-24
!
controller T1 0/0/3
cablelength long 0db
channel-group 0 timeslots 1-24
!

interface MFR34
mtu 4470
no ip address
no ip redirects
encapsulation frame-relay IETF
frame-relay multilink bid u11111-11
frame-relay lmi-type ansi
!
interface MFR34.500 point-to-point
description multilink:MLFR:3xT1
bandwidth 6000
ip address x.x.x.x x.x.x.x
ip nat outside
snmp trap link-status
no cdp enable
no arp frame-relay
frame-relay interface-dlci 500 IETF
!

interface Serial0/0/0:0
mtu 4470
bandwidth 1536
no ip address
no ip redirects
no ip proxy-arp
encapsulation frame-relay MFR34
load-interval 30
cdp enable
no arp frame-relay
!
interface Serial0/0/1:0
mtu 4470
bandwidth 1536
no ip address
no ip redirects
no ip proxy-arp
encapsulation frame-relay MFR34
load-interval 30
no arp frame-relay
!
interface Serial0/0/2:0
mtu 4470
bandwidth 1536
no ip address
no ip redirects
no ip proxy-arp
encapsulation frame-relay MFR34
load-interval 30
no arp frame-relay
!
interface Serial0/0/3:0
mtu 4470
bandwidth 1536
no ip address
no ip redirects
no ip proxy-arp
encapsulation frame-relay MFR34
load-interval 30
no arp frame-relay
!

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