HSRP config

[sarsamivel]

Folks

We are planning for redundancy setup between 2 sites.Attached the router setup bw sites.

Can let me know if HSRP can be configured between R1 and R3.If so,how ?

SAM

[crow930us]

HSRP support for Multiprotocol Label Switching Virtual Private Networks (MPLS VPNs) was added in Cisco IOS release 12.1(3)T.

HSRP on an MPLS VPN interface is useful when you have an Ethernet connected between two Provider Edges (PEs) and you have either of the following:

* A Customer Edge (CE) with a default route to the HSRP virtual IP address.

* One or more hosts with the HSRP virtual IP address configured as the default gateway.

This tech note should have more info: http://www.cisco.com/en/US/tech/tk648/tk362/technologies_tech_note09186a0080094a91.shtml#hsrpsupport

[sarsamivel]

I shud hav given more info on the setup.

R1 and R3 are managed by service providers.R2 and R4 are managed by customer.

R1,R2 in Site A and R3,R4 in site B.

currently R1 and R2 are in HSRP and same as R3 and R4.

Now we wanted to utilize both MPLS links at site A and B for Site A traffic.like Active-Active setup,same time need redundancy in setup.How can we acehieve this?

let me know if more info needed.

Thanks in advance

SAM

[Giuseppe Larosa]

Hello Sam,

if multiple hosts are present in each client vlan you can use GLBP.

see

http://www.cisco.com/en/US/docs/ios/ipapp/configuration/guide/ipapp_glbp_ps6350_TSD_Products_Configuration_Guide_Chapter.html

the requirement is that all devices have to be Cisco devices because it is a proprietary protocol.

if the device in the client is only one you can use multiple HSRP groups and you can double each static route using as IP next hops the two VIPs

tracking of interfaces or using ip sla objects is possible with both protocols and completes the solution (preemption is needed )

Hope to help

Giuseppe

[sarsamivel]

Hi Giuseppe,

Is it possible to configure MHSRP on R1 and R3 in ths scenario and provide redundancy as well load balancing.

I know HSRP works on ethernet,will i be able to bring R1 and R3 in same LAN ?

Thanks

SAM

[Giuseppe Larosa]

Hello Sam,

R1 and R3 are the routers under your control but they are in different sites.

the proposal is for routers on the same site: you should coordinate the changes with who manages R2 and R4 in order to achieve load balancing for traffic between the two sites (both directions)

Without involving the people who manages R2 and R4 there is little you can do: you can have R1 and R3 active routers for the existing HSRP group but this is not enough to achieve load balancing.

Hope to help

Giuseppe

[sarsamivel]

Hi Giuseppe,

If i have 2 equal cost routes to same destination,to what extent i can acheive loadbalacing?

What changes i need to make at other end?I have to configure two equal cost route via two links back to the source,is tht right ?

Thanks

SAM

[Giuseppe Larosa]

Hello Sam,

your understanding is correct

to achieve load-balancing you need two equal cost paths.

on both directions = on both sites

for end users GLBP provides load balancing at the ARP level.

the right tool to use depends on your scenario details.

Hope to help

Giuseppe

[sarsamivel]

Hi Giuseppe,

Thanks for guiding me.one more question.

How does equal cost path routes perform load balancing?Can we acheive perfect load balance b/w two links.?

SAM

[Giuseppe Larosa]

Hello Sam,

once there two paths installed in the routing table CEF performs load balancing.

Standard CEF load balancing is per flow

the two paths are logically numbered 0 and 1

(IP SA last bit) Exor (IP DA last bit) Exor Hash_seed

provides a 0 or 1

flows with IP SA and DA that gives result 0 are sent out path 0, flows whose IP SA and DA gives result 1 are sent out path 1.

If your traffic is enough variable: it is made of many low volume traffic flows the balancing results are good.

if there is a single very high volume flow (example a DB synchronization) all packets of the flow use a single link

Hope to help

Giuseppe

[sarsamivel]

Hi Giuseppe,

Will the return traffic will use the same path per flow.

by FLOW,i understand it's a TCP session ?

We will have only RDP,Telnet and Management traffic on these links.Shud there be an issue on latency?

Thanks,

SAM

[Giuseppe Larosa]

Hello Sam,

no each device choices how to send packets so it is possible that return traffic takes the other path.

A flow is direction specific for CEF forwarding purposes.

Hope to help

Giuseppe

[sarsamivel]

Hi Giuseppe,

Based on your experiences do you see any issues for Management protocols like telnet,RDP etc when the response comes thru second link.This link will have additional latency of 10ms to the site.

Thanks

SAM

[Giuseppe Larosa]

Hello Sam,

I don't think this delay difference (10 ms) can be an issue for Telnet or RDP and other TCP based applications.

Hope to help

Giuseppe

[sarsamivel]

Thanks Giuseppe.It was much helpful.