layer 2 redundancies

[penghon]

Other than having 2 links between 2 switches with one in blocking due to spanning tree + uplinkfast turned on (suppose to up the standby link in 1-5 minutes), is there other L2 redundancies (instead of STP) can i implement?

 

[ADB100]

EtherChannel would be my first suggestion. With Catalysts you can bundle multiple ports of the same type into an EtherChannel creating an aggregate link that can be up to 8-ports. So for FastEthernet you can have a potential 800Mbs full-duplex link between 2 Catalyst switches. The way traffic is split over the links is done using an algorythm based on ether Layer-2, Layer-3 or Layer-4 information, so traffic isn't broken up and split over the links, but send down a particular channel based on the address information in the packet.

http://www.cisco.com/en/US/partner/tech/tk389/tk213/tech_protocol_family_home.html

Best of luck

Andy

 

[penghon]

Yup, I have considered etherchannels but it only provided redundancies in the event that all traffic will be carries by the remaining working channels. If one of the switches goes down, the etherchannel is broken, hence no redundancies in this case.

 

[ruster]

What is the layer 2 scenario that you are seeking. If you have a stack of switches dual homed to a core switch, in the event that a single unit fails, the remaining units will continue to forward traffic as required. Etherchannel is generally a layer 2 redundancy feature for a server or critical device, whereby you are trying to protect against a nic failure. HSRP would be used for layer 3 gateway redundancy. Be a little more specific on what your needs are, and we may be able to come up with additional suggestions.

Ruster
CCNP,CCDP,CCEA,CWNA,MCSE

 

[penghon]

Well, a have a bunch of 3548 with 2 gbic slots hooked to 2 4003s. Currently the redundancy is zilch. I have 2 options: 1) etherchannel to one of the cores, or 2) one fiber link to each of the 4003.

Any other ways for redundancy? NO L3...a purely L2 network.

Thanks in advance...

 

[ADB100]

Are the 4003's link together? I assume they are based on your comment '...NO L3...a purely L2 network'. I would look at a redesign to be honest, unless you are running non-routable protocols or legacy stuff (Appletalk, DECNet etc).
Single link from each 3548XL to each 4003, then get some L3 going on.........

Andy

 

[baddos]

I can't think of anything other than what you have mentioned....

BTW... Why is the spanning-tree reconfiguration time a problem for you? If a whole 4003 goes down, you'll be loosing a lot of your network. 10-30 seconds on downtime for the edge 3548's doesn't seem that bad.

If you wanted to go with other vendors for your switches, some of them offer port trunking (like cisco etherchannel) accross diffrent chassis. The only cisco switch that supports this is the really expensive 3750.

 

[penghon]

Apologies for missing out some info...the 2 4003s are linked up via juz one fiber link (i am planning to add in one or two more fiber links to form an etherchannel for redundancies). There are a bunch of vlans running all over. If i have a 3550-SMI, where would i wan to put it in?

As for redesigning the network, it is possible but I dun really have any idea what is the best approach or what is the industry best practice.

Any suggestions?

 

[clahnum]

http://routergod.com/paulhogan/let's

talk about the Hot Standby Router Protocol. HSPR is a way for two Cisco routers to share a common virtual IP address while one router is actively routing packets, the other router or routers are standing by in case the active router fails. It's a very good way to provide fault tolerance. In fact, if ya take a mind to, you can read RFC 2281 to learn a bit more about it.

So the routers share an IP address. How do the routers know when one has failed?

Let's get back to the IP address, besides sharing an IP address, that IP address has a common MAC address that the routers share. It's like this, mate, you have a workgroup of say, I don't know, 100 computers. Each one of these machines has been configured with a default gateway, if these machines have used the default gateway or router, they have it's MAC address in their ARP cache. So since the routers in the HSRP group share an IP address with a corresponding MAC address, when they fail over, the workstations are unaware of the change. What they see, is a "virtual" router.

the routers in an HSRP group send and receive keep alives using the multicast address of 224.0.0.2 and UDP port 1985. By default the hello interval is 3 seconds. Once 3 hello intervals pass without hearing from the active router, the standby router automatically becomes the active router. Each router is configured with a priority number, the router with the highest priority number in a standby group is the active router, everyone else just relaxes.
you only need 2 commands to do it, and 2 additional commands to customize it. What's more, it's configured at the interface that you want to participate in the standby group.
Well, first off, on the router that you want to be the active router, go to the interface you want HSRP to run on, think up a group number, all routers participating in this scheme must use the same group number, also think up what IP address you want the HSRP group to share. Now watch me type:

dingo(config-if)#standby 1 ip address 10.1.1.254
dingo(config-if)#standby 1 priority 100

So what we have here mate, is a standby group number of 1, an IP address of 10.1.1.254 that the routers are going to share, now let's configure the standby router:

fosters(config-if)#standby 1 ip address 10.1.1.254
fosters(config-if)#standby 1 priority 90

OK, the only thing different on the standby router is the priority. The router with the highest priority becomes the active router.

 

[penghon]

Please read the earlier posts, we are talking about L2 redundancies, not L3...