Load Balancing doubts

[cisco]

Hi,

I am having doubts regrding load balancing , so i am summarising all the scenario . Kindly share your inputs

load balancing of user data from LAN towards WAN

Scenario 1) one router connected to a SP with dual links

Solution) By default it will be achieved by Per-Destination Load Balancing

Scenario 2) one router connected to 2 SPs

Solution )HSRP can be also used or ONLY BGP can be used ? if BGP, then which attributes can be used ?

Scenario 3) Two router connected to single SPs

Solution) HSRP/VRRP/GLBP

Scenario 4) Two routers connected to 2 SPs with single link each

Solution) Only BGP?

regards

Neo

[Marwan ALshawi]

Good question !

first of all you need to understand that from the router/routing point of view there is no difference if the multi homing with one or two differnt ISPs ( expect for some BGP attributes )

- if  you have router connected to a certain ISP/ISPs with dual links then first of all you need to make sure that in you RIB/routing table you have two equal cost ( unequal support with EIGRP) routes using both interfaces

like two default routes each one using diffrent links

- if the routing protocol is BGP then you need to enable the max eibgp multipath command ! to let the BGP install multiple paths for one routing ( assuming all other BGP attributes are equal ! )

- if you have two routers in your end and yu want to use HSRP/BLBP then here you are not using the routing protocol for load balancing or per destination algorithm however you are relaying of FHRP like HSRP or GLBP to load balance or share the traffic, which is diffrent concept

wish this will help you understand it in high level

good luck

if helpful Rate

[cisco]

Hi,

After reading your response , i have reached to this conclusion (My understanding marked with *)

Scenario 1) one router connected to a SP with dual links 

Solution) By default it will be achieved by Per-Destination Load Balancing

* If i have two equal cost links then its possible. This solution is fine

Scenario 2) one router connected to 2 SPs

Solution )HSRP can be also used or ONLY BGP can be used ? if BGP, then which attributes can be used ?

*HSRP can't be used , BGP will be used where i have to enable the max eibgp multipath command and to let the BGP install multiple paths .

Scenario 3) Two router connected to single SPs

Solution) HSRP/VRRP/GLBP

*This is possible , but same routing table should be there on both the routers.

Scenario 4) Two routers connected to 2 SPs with single link each

Solution) Only BGP?

* I didnt get the solution for this

regards

Neo

[Giuseppe Larosa]

Hello Marwan,

nice to see you again in the forums

in order to install BGP routes coming from two different ASes/ISPs an hidden command is needed when dealing with standard eBGP sessions ( address-family ipv4 unicast)

bgp bestpath as-path multipath-relax

as explained in several posts in the forums

see

https://supportforums.cisco.com/message/790535#790535

for original poster:

scenario 1) : maximum-paths 2 under router bgp is enough, if the router is only one no need for HSRP/VRRP/GLBP on the internal interface

scenario 2) described above needs two commands on border router. Again

if the router is only one no need for HSRP/VRRP/GLBP on the internal interface

scenario 3) iBGP session between border routers help

scenario 4) requires eBGP sessions and iBGP session between the border routers

Hope to help

Giuseppe

[Marwan ALshawi]

Thanks Giuseppe I was busy with work

You right about bgp commands but I just provided quick high level description

One important think for the original post is that you need to distinguish between routing and fhrp like hsrp they are different protocols and concept !

for having loadbalancing with two routers each connecting to a different ISP u can use cisco performance routing PfR

Each routing protocol has different configuration for multipathing however they almost share the same concept and logic except with EIGRP as it support unequal cost lb

Wish this will help you

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