Fractional T3 Frame Circuit config. 1

[tdoma]

I have beginner's skills for cisco router configs. I have been asked to configure a new fractional T3 frame connection for internet access. I will be using 2600 router with 2 T1 WICs. The ISP has terminated 2 T1 lines into our building. This link will be replacing the existing single T1 connection from the same ISP. From a configuration standpoint, other than the 2 DLCI numbers, is there anything that I will need to configure so that the 2 circuits can be utilised simultenously?

 

[sg4me]

Hi Tdoma,
First thing first, 2 T1’s do not equal a T3. There is a world of difference between a 3 Mbit (2xT1) connection and a 45 Mbit (1xT3) connection.

However, I can help. If you are using a bonded T solution which it sounds like you are, you should get a Multiflex Trunk T1 VWIC (Part number: VWIC-2MFT-T1). This allows the two T1s to be bonded together into one 3Mbit connection. However, you need a Cisco 2620 router or above. My firm is currently implementing two of these types of connections over the next 30 days at two of our locations. I can’t tell you how well they work or exactly how to do it as the consultants from our Telco provider has not provided us with the configurations yet.

Hope I helped some,
Ben

 

[IllegalOperation]

Sg4me, why not use the multilink feature imbedded with the router's IOS? Instead of having additional hardware bond circuits together, I think it would be more cost effective to use MLP.

With MLP, you can add and delete T1s as you wish...up to ten total. You can only have a maximum of two ciruits with a VWIC-2MFT-T1, and when you add or remove ciruits (downgrading or upgrading) - you are still stuck with that WIC card....

 

[tdoma]

IllegalOperation. Do you have any pointers on how to configure the multi-link feature on a 2610XM router? Are there documents you can point me to?
Thank you in advance for your help.

 

[IllegalOperation]

I apologize tdoma, I didnt notice your reply. This should work...

http://www.cisco.com/univercd/cc/td/doc/product/aggr/10000/10ksw/mlppos.htm

 

[nyy1023]

IllegalOperation...you get another star!!!
Just to add one more thing...make sure that the ISP you are connecting to will run MLP.
The one I use to work for, which had a lot of finacial issues and close my office and put me out on the streets to live in the dumpster behind my daughters school...oops too much info, sorry!
MCI, well at least as of may '03, did not run MLP. I am not sure if there are others out there, but just double check to see if you can run this feature with them.

 

[tdoma]

I would to add that while I was sharing the above solution with my immediate supervisor, he suggested that I also take a look at CEF & or Equal Cost Load-Balancing (if different from CEF). My questions to the more experienced Cisco guys, is there a document that enumarates the pro & cons of either solution? If the goal was to increase the amount of available bandwidth (>1.54MBPS) and provide fault tolerance at the same time, what would be the preferred solution given the information above and the original post?

Thanks again for your support.

 

[nyy1023]

Equal is a bad word.
You can share the lines, but will be very lucky to get 50/50
BGP can give you this, and setting up route-maps to add metrics to the routes.

I would go the BGP route myself. Only because I am very familiar with it.

 

[tdoma]

Sorry to bother you, but I am not sure I understand your response. Are you suggesting that I go with CEF, or are you saying I should stick with MLP? Does MLP offer fault tolerance as well? Between CEF and MLP, which solution would provide both fault tolerance, + higher bandwidth, preferably higher than we would normally get from a single T1 circuit? Any pointers on documentation that states the pros and cons of either solution?

Thank you again for your help.

 

[mtashiro]

CEF improves throughput, in simple terms, by making routing decisions quicker. Routes are looked up in the CEF table and not the routing table.

MLP will increase bandwidth and provide redundancy.

If your router does not have a lot of memory you should probably not use CEF unless your routing table is small.

 

[IllegalOperation]

You are right nyy1023 about MLP, your ISP does have to support it. Strange how both MCI and SBC do NOT support this feature, eh? Would be much more convenient for us groundlings. (Thanks for the star by the way, you get one as well)

Anyways, here is some additional info about load sharing (cef per destination and per packet) - which is pretty much your only other viable software solution....

http://www.cisco.com/en/US/products...figuration_guide_chapter09186a00800ca62c.html

http://www.cisco.com/en/US/products/sw/iosswrel/ps1829/products_feature_guide09186a0080087c5b.html

I suggest to do per destination instead of per packet, but that also depends on what your specific network needs are. Also, I wouldnt recommend doing BGP in your scenario - as not only do you need a registered AS#, but a /24 block as well. The biggest reason why I dont recommend BGP for your solution is you only have a 2600 series router, which I doubt would be able to handle it.

First things first, I would ask your provider if they support MLP...

 

[tdoma]

Update.
I have been informed by our ISP that they do not support MLP, so it is going to be CEF.
Other than adding the specifc commands for CEF, is there anything else I will need to add the existing config on the production router? The running config is:

!
version 12.2
service timestamps debug uptime
service timestamps log uptime
service password-encryption
!
hostname CARE-INTERNET
!
enable secret 5 $1$fGd4$UDAA/bTu1FWBqYzoX.xkn1
enable password 7 031752070301224541
!
memory-size iomem 20
ip subnet-zero
no ip source-route
!
!
no ip domain-lookup
ip name-server 205.214.45.6
ip name-server 205.214.45.1
!
!
!
!
interface Ethernet0/0
ip address 155.229.204.1 255.255.254.0
no ip route-cache
no ip mroute-cache
half-duplex
!
interface Serial0/0
ip address 155.229.99.30 255.255.255.252
ip access-group 101 in
no ip unreachables
no ip route-cache
no ip mroute-cache
no fair-queue
!
interface Serial0/1
ip address 209.101.202.218 255.255.255.252
ip access-group 101 in
no ip unreachables
no ip route-cache
no ip mroute-cache
no fair-queue
!
ip classless
ip route 0.0.0.0 0.0.0.0 209.101.202.217 10
ip route 0.0.0.0 0.0.0.0 155.229.99.29 10
no ip http server
!
access-list 12 permit 155.229.204.40
access-list 101 deny icmp any any echo
access-list 101 permit ip any any
access-list 181 permit ip host 24.98.227.128 host 155.229.204.70
access-list 181 permit ip host 155.229.204.70 host 24.98.227.128
snmp-server community nopublico RO
snmp-server enable traps snmp authentication linkdown linkup coldstart warmstart
snmp-server enable traps tty
snmp-server enable traps hsrp
snmp-server enable traps config
snmp-server enable traps entity
snmp-server enable traps envmon
snmp-server enable traps bgp
snmp-server enable traps ipmulticast
snmp-server enable traps msdp
snmp-server enable traps rsvp
snmp-server enable traps rtr
snmp-server enable traps syslog
!
line con 0
exec-timeout 0 0
line aux 0
password 7 02000D490E040E2D40
login
modem Dialin
modem autoconfigure discovery
autohangup
speed 38400
line vty 0 4
session-timeout 90
access-class 12 in
password 7 13081615020F0C2F2734
login
!
end

Thanks again for your help and patience.

 

[IllegalOperation]

Yes, your WAN interfaces are missing critical information.

I am assuming your provider will use frame. You need to configure the encapsulation (most likely IETF), the amount of timeslots used (most likely all if you purchased the full circuit, 1-24), and the lmi type (most likely ANSI). In addition, it is common practice to create a serial subinterface (not absolutely needed all the time, but much easier administratively) for each specific link. On the subinterface is where you configure the dlci identifier, bandwidth the circuit is set for, and the ip address. All of the needed information should be given to you by your provider beforehand.

I believe that are the only requirements to run the circuit, but there are also additional configurations that you may need to suit your purposes. Hope that helps...

 

[jdel]

just a quick note isn't IETF encap and ANSI lmi type chosen by default on cisco routers?

 

[Cluebird]

Nope. Cisco chooses Cisco encap by default so you have to specify IETF either globally or per dlci (depends on how you've configured your frame). The lmi is auto-sensed on IOS above 11.2.

 

[jdel]

ahh you're right. thanks

 

[tbilan]

I've used BGP, CEF and MLP to increase bandwidth and I like CEF the best. If you set it up on a per-packet base it will give you darn near 50/50 balancing. You'll have to make sure the ISP puts your 2nd circuit on the same routers as the first, preferrably the same line card.


Tom Bilan
TJBA, Inc.
CCNP, CCDP, MCSE & CNE