Bonding T1s

[dayhawk]

I have 2 T1 point-to-point connections between my central office and a remote site. I have a 1761 at the central office and a 1721 at the remote site. I want to take these 2 T1 1.5 Mbps circuits (from the same ISP) and bond them into 1 virtual circuit. I have a dual-WIC in each router to terminate each T1 circuit at each end. How would i go about bonding these circuits? Thank you.

 

[BuckWeet]

You can't bond them, but you can do equal weighted routes, that way it'll load balance across the two..

BuckWeet

 

[baddos]

I've never done it, but you can try Multilink PPP.

Here is some documentation on it.

http://www.cisco.com/en/US/products...ion_guide_chapter09186a008008730a.html#wp3729

 

[dayhawk]

Thanks for the input guys. If bonding wasn't the correct term, what does it mean? Here's what I plan to do:

<example config>

interface Multilink1
ip addres 192.168.1.1
no cdp enable
ppp multilink
multilink-group 1
!
interface Serial 1
no ip address
encapsulation ppp
no fair-queue
ppp multilink
multilink-group 1
!
interface Serial 2
no ip address
encapsulation ppp
no fair-queue
no ip route-cache
ppp multilink
multilink-group 1
!

Any more ideas would be most helpful and greatly appreciated.

 

[TheMoogy]

The config is correct and will work, we use multilink groups on a number of sites without any problems. Just remember to point the IP routes at Multilink group or use a routing protocol such as EIGRP.

 

[IllegalOperation]

Dayhawk, bonding is the correct term for multilink PPP. It logically &quot;bonds&quot; the two circuits, making them appear to the outside world as one. However, PLEASE check with your ISP to make sure they support that feature. There are plenty of carriers that DO NOT support MLP. SBC and MCI are two of those companies, for example.

You have pretty much two other acceptable options if you cant use MLP. The first one is inverse multiplexing technology, which uses hardware to &quot;bond&quot; the circuits. You will also have to check with your provider for that service, as it is not very common in my opinion.

The second option is the use of Cisco Express Forwarding (CEF), which I believe is what BuckWeet was trying to say. CEF is sofware driven, memory intensive, and does NOT combine the circuits. It simply distributes the load among the two links - either by destination or by packet (your choice). It is not a true form of load sharing, but it is pretty much close to it. Please note that with CEF, your maximum speed will still only be 1.544Mbps....as some people believe you can get faster speeds. You should also verify with your ISP about the use of CEF, but I have yet to see a major telco not support that feature....

 

[dayhawk]

Thanks for all the helpful information guys. I guess CEF is out for me since the whole purpose of this project is to obtain a 3Mbps circuit.

 

[IllegalOperation]

Well you do have to realize that with CEF, your traffic is virtually balanced out the two links - so in essance you will be able to handle twice the load. Even though it doesnt increase the max possible speed, it still greatly enhances your network's performance - especially if your lone T1 was overburdened.

You might want to check into fractional DS3s. I have noticed that the prices have recently decreased dramatically....

 

[dayhawk]

How would i go about accomplishing the same thing but with T1 Controller cards installed in the router? Current out-of-the-box config:

version 12.3
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname SWMC1721
!
boot-start-marker
boot-end-marker
!
enable secret 5 $1$97z1$R942NY2BsUdovjwj775Rn1
enable password ciscot1
!
no aaa new-model
ip subnet-zero
no ip routing
!
!
!
!
no scripting tcl init
no scripting tcl encdir
!
!
!
controller T1 0
framing esf
linecode b8zs
!
controller T1 1
framing esf
linecode b8zs
!
!
interface FastEthernet0
ip address 10.13.14.10 255.255.255.0
no ip route-cache
speed auto
full-duplex
!
ip classless
no ip http server
!
!
!
control-plane
!
!
line con 0
line aux 0
line vty 0 4
password ciscot1
login
!
no scheduler allocate
!
end