03-17-2004 09:26 PM - edited 03-02-2019 02:22 PM
Here is the setup:
I have two sites: LAN1 is connected to LAN2 by 2611XM on each side and both router connected to each other with two WIC Point to Point T1.
I like to know what is the best way to load balance trafic between two sites.
- Jayesh
03-17-2004 10:28 PM
IP CEF will do what you are looking for. What sort of traffic are you sending? You can do per-packet load balancing, but that is not recommended if you are sending delay sensitive traffic, such as voice.
Reference - Cisco - Configuring CEF -
03-18-2004 10:06 AM
Jayesh -
You don't need to use CEF if you don't want to. You can still do per packet or per destination load balancing without CEF too using 3 different methods.
Since these connections are back to back a Dynamic protocol probably isn't needed. You could just configure two static routes to the same destination on both routers and just point each route out a different PTP T1 interface.
For per packet load balancing which means the router will do a route table lookup (more CPU intensive and more delay) on your Ethernet LAN interface and T1 interfaces put in the command "no ip route-cache" to disable fast switching.
For per destination load balancing which means when the router receives a packet it examines the destination and looks up a fast-switch cache, if the router does not have an entry for the destination the L3 routing engine does a regular routing lookup and makes a forwarding decision. After this lookup is done the cache entry is created so subsequent packets to the same destination will just use the cached entry by passing the routing table lookup process.
Use PPP multilink which will bond the t1's together and automatically do fragmentation/load balancing on the PTP t1's.
Sample PPP Multilink config -
Site A
interface multilink 1
ip address 10.10.10.1 255.255.255.252
ppp multilink
multilink-group 1
!
interface serial 0
no ip address
encapsulation ppp
ppp multilink
multilink-group 1
!
interface serial 1
no ip address
encapsulation ppp
ppp multilink
multilink-group 1
Site B
interface multilink 1
ip address 10.10.10.2 255.255.255.252
ppp multilink
multilink-group 1
!
interface serial 0
no ip address
encapsulation ppp
ppp multilink
multilink-group 1
!
interface serial 1
no ip address
encapsulation ppp
ppp multilink
multilink-group 1
Verify PPP multilink using "show ppp multilink".
This link will show you how to do PPP Multilink with a Virtual Template interface which accomplishes the same as above. I have used both methods and haven't had any preference on either one because they both work just fine.
Daniel
03-18-2004 12:49 PM
Daniel,
Thanks for the information,
Does multilink provide redundancy also? If one line fails does trafic still forwarded on other line?
Jayesh
03-18-2004 02:36 PM
It sure does.
03-18-2004 03:09 PM
Jayesh,
Yes I'm sorry I didn't add that into my remark. The way multilink works is it creates a master interface that is responsible for the links (t1 interfaces) which in multilink is called a bundle.
If you have multilink enabled and a particular link fails, traffic will simply stop flowing across that pipe and multilink will remove it from the bundle.
Once it comes back up again multilink will add it to the bundle and begin to use the pipe again.
So it provides load balancing, redundancy and fault tolerance.
Daniel
03-19-2004 12:08 PM
Do I need to add static route for destination LAN?
LAN1 and LAN2 are connected with routers on both side. I am using EIGRP and IP CEF is enabled.
Thanks
Jayesh
03-19-2004 12:57 PM
If you are using EIGRP you don't need to input any static routes.
Daniel
04-05-2004 01:29 PM
Daniel,
I have configured router as follow. Let me know if it should work or any change need to be made.
Router A:
!
ip cef
!
interface FastEthernet0/0
description "Interface to LA LAN"
ip address 172.15.3.1 255.255.0.0
speed 100
full-duplex
!
interface Serial0/0
ip address 10.10.1.1 255.255.255.252
ip load-sharing per-packet
shutdown
fair-queue
service-module t1 clock source internal
service-module t1 timeslots 1-24
!
interface Serial0/1
ip address 10.10.1.5 255.255.255.252
ip load-sharing per-packet
shutdown
fair-queue
service-module t1 clock source internal
service-module t1 timeslots 1-24
!
router eigrp 1
redistribute static
network 10.0.0.0
network 172.15.0.0
no auto-summary
no eigrp log-neighbor-changes
!
ip classless
ip route 0.0.0.0 0.0.0.0 172.15.1.1
Router B:
!
ip cef
!
interface FastEthernet0/0
description "Interface to SF LAN"
ip address 172.16.3.54 255.255.0.0
speed 100
full-duplex
!
interface Serial0/0
ip address 10.10.1.2 255.255.255.252
ip load-sharing per-packet
shutdown
fair-queue
service-module t1 timeslots 1-24
!
interface Serial0/1
ip address 10.10.1.6 255.255.255.252
ip load-sharing per-packet
shutdown
fair-queue
service-module t1 timeslots 1-24
!
router eigrp 1
redistribute static
network 10.0.0.0
network 172.16.0.0
no auto-summary
no eigrp log-neighbor-changes
!
no ip http server
ip classless
ip route 0.0.0.0 0.0.0.0 172.16.1.1
04-05-2004 02:42 PM
It looks like it should work. Just remember to turn on the serial interfaces.
Once you have the routers in place make sure a "show ip route" shows two routes to the same destination using two different next hop IP addresses.
"Show ip eigrp topology" should also show two successor routes to the same destination.
Daniel
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