Route Recovery on a L2 Switch for link failure on network

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junecore

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Hello All,

I am trying to setup a network redundancy for a streaming media server.
I am more worried about link breakage, rather than equipment failure.
There are Five Subnets: 1 Server subnet and 4 Host subnets.
Each S/switch has two 1GB uplinks going to either another switch
or Router1/2.

The setup is as follow:

Server1 (HA) Server2
|_______________|
.............S0 Subnet0
..............|
._---------------------_
|................................|
R ---S1---s1--s1--S1--- R ... Subnet1
o.................................o
u ---S2---s2--s2--S2--- u ... Subnet2
t.................................t
e ---S3---s3--s3--S3--- e ... Subnet3
r..................................r
1 ---S4---s4--s4--S4--- 2 ... Subnet4

I want to setup :

1. Route Recovery between S/Switch links.
So if link going to Router1 goes down Link to Router2
should take over and continue the media streaming without
any or very small amount interuption. This setup is more
to protect from link failure rather than switch failure.
What type of setup is commonly used for this kind of network?
Again, the switch has two ports that will forward the traffic
to either router1/2 and later the traffic will be send to S0
(switch in subnet0).
2. Route priority on Routers to reach the live server.
Each row of S#/Swithes is its own subnet. I am not much familiar
with clustering and HA senerio. So please give me some basic guidance
on what i need to do on network side for this kind of clustered setup.

Let me know if you need more information.
 

zx10guy

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Could you include a better diagram? The one you've posted is a bit confusing. For layer 2 link redundancy, you have a couple of options depending on how many switches you have and how they're laid out. You can use Etherchannel/LAG groups for one mode of link redundancy. Or you can play around with spanning-tree and leverage priority tagging to define a preferential direction for the inter-switch traffic to flow. I did exactly the latter with a setup I have here at work with two Cisco Catalyst 6509 switches both running in a HA stack connected to a single access layer switch for developer access. Setting the spanning-tree priority of each switch allowed me to have both switches attached to the access switch, and created a standby failover setup. The other parameter I set to tweak the speed at which the failover link comes up was to set the forwarding time to 4 seconds (the lowest speed allowed by Cisco.)

Testing the connection only had a maximum of two dropped packets before the other link went from a blocking state to a forwarding state. Restoring the primary link, caused all traffic to roll back over to the primary link and caused the secondary link to go back to a blocking state which is what I wanted. Doing it this way prevents any switch loops form occurring.
 

junecore

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The switches between 2 routers have two up links going opposite direction one to Router1 and another to Router2. So what features to use to make sure that the link failure is detected and alternate route is setup with minimum downtime to the user. Will this feature be also supported on Routers?

I was thinking about MSTP and VRRP. Have you any thoughts on these features.

THnaks again for your comments.
 

zx10guy

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How many switches do you have? Are they wired to each other in any fashion? What is the purpose of these two routers? What are they routing to on the WAN side?
 

junecore

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the switches are configured as such:

S1_p1.1 ( 1GB port ) linked to Router1
S1_p1.2 ( 1GB port ) linked to s1_1.1 (1gb port )
S1_p0.1 to S1_p0.24 are for host connections.
Basically daisy chained between other switches.

I have a image but cannot attach the picture here. :mad:
Hub1 <---> R1<--> [ S1_1.1 -- S1_1.2 ] <---> [ s1_p1.1--s1_p1.2 ] <---> [S1_p1.2 --S1_p1.1 ]<--> R2 --> Hub1
hope this clarifies things...

router are there for redundant routing and there is no WAN connection, Just another subnet to Server Subnet.
 

zx10guy

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So from the router stand point, it depends on what routers you are dealing with. Are these Cisco routers? If they are Cisco routers, you have two choices: either HSRP or GLBP. I'll have to look to see if there's VRRP support but if they're both Cisco, there's no need to run VRRP as HSRP will do the job equally as well.

As far as the switch layout, I'm still confused with your use of S1 and s1. How many switches are we talking about here? 2, 3, 4......?
 

junecore

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There are around 5-6 switches on each subnet.

yeah I was wondering about VRRP too.
How is this different than HSRP? And will that give me Redundent Routes in case one of the router fails ?
 

zx10guy

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HSRP is Cisco's implementation. So what brand of routers do you have? And are these switches you have managed? When you talk about redundant routes, what do you mean exactly? HSRP and VRRP gives router redundancy. If you're looking for alternate route path redundancy, you're going to have to run some sort of routing protocol. But in a network this simple, it'll do very little to help you. When you mention subnets, what's your subnet scheme? Do you have VLANs running? Do you have secondary addresses running on your router's internal interface? Are you using sub-interfaces on your router?

A network diagram will really help in getting a better picture of what we're talking about here.
 

zx10guy

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Based on the diagram and making some assumptions which is your layer 2 network is properly laid out, all you would need to set up is HSRP or VRRP at both the client side router interfaces and at the server side interfaces. If you want more assurance of a particular interface being reachable or operational on a specific router, you can institute an SLA layout as defined by Cisco which involves things like tracking a specific IP reachable by the interface to ensure full network functionality.
 

junecore

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Thanks for your info.

FYI: I am not using a Cisco router. But a L3 that supports VRRP. So I can use that for Route Redundancy.

But on Layer2 (switches), I am worried about broadcast storms that will be created by STP. How can I setup L2 such that it will have two up-links to choose but will not create loops when STP is advertising? I was thinking about setting up multiple MSTP instances on each subnetted ports on router side to prevent loops.

Is there something that could help me to reduce STP traffic-related broadcast storms on the L2_Switches besides creating MSTP instatances on the each subnetted Router Ports.


Thanks again for everything.
 

zx10guy

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I'm not sure how you have your switches wired up. But you can play around with the priority setting in spanning-tree on each switch to create a preferrential layer 2 path.
 
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