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help reqd in private BGP

spremkumar
Level 9
Level 9

Hi all

i need some info on the given scenario(private BGP) ..

customer is having 2 Corp offices one @ location A and second one @ location B.

At Loc A hes having IBW with one SP and at Loc B with some other SP.

Hes having interlinks between 2 of his locations i.e., Loc A&B.

so using tht link he wants to have redundant Internet connecitivity.

Related to SP setup all the IBW are configured in Core Routers and the customer links are connected to other Edge router on Both the SPs.

Core routers are running BGP(both I and E) but the Edge routers arent at this moment.

To create PBGP we are planning to run PBGP in tht router where the customer is connected to both the SPs..

Wht steps to be followed to design a robust,reliable config so tht it can solve the purpose for which its configured ..

Regds

prem

19 Replies 19

ruwhite
Level 7
Level 7

It seems like you shouldn't need BGP between the two sites in this case, if I understand what you are trying to do, ad how the network is set up. I would just send a default from each edge conditioned on the connection to the ISP--one way to do this would be to receive a default from each ISP, and redistribute it out to the IGP being used in the network. Another way would be to crate a static pointing to the interface which connects to the ISP (given it's not a broadcast network of some type--static defaults pointing to broadcast networks, like ethernet, are not a good thing), and then redistribute that static into the IGP being used.

Russ.W

ruwhite
Level 7
Level 7

It seems like you shouldn't need BGP between the two sites in this case, if I understand what you are trying to do, ad how the network is set up. I would just send a default from each edge conditioned on the connection to the ISP--one way to do this would be to receive a default from each ISP, and redistribute it out to the IGP being used in the network. Another way would be to crate a static pointing to the interface which connects to the ISP (given it's not a broadcast network of some type--static defaults pointing to broadcast networks, like ethernet, are not a good thing), and then redistribute that static into the IGP being used.

Russ.W

hi rus

we r not insisting the cust to run PBGP but its the other way.Main reasons told to us r reduandancy via both sides.they hve 1Mb on both the sides so as to hve a proper bckup they r going for the same.

both the sps r running ospf between their core and edge where the customer is conencted.

thru ospf i m getting the default route in edge routers so i dont think we need to send the routing info to customer.better to point dafault route pointing towards one SP and one with metric pointin their interlink.

my point of concern here is at Location A hes using ISP A and location B hes using ISP B.

For ISP A ISP B is the upstream provider.

at Location B hes using ISPBs address space and in location A ISPAs.my question here is how i can advertise ISPBs address block which is ther lcoation B to ISPB hre in Location A ??can it be done like tht ??i dont hve any problems on the other side since i m going to advertise ISPAs block to ISPB @ loc B.

prem

Some questions please:

Do you NAT private addresses to the ISP address blocks?

Do you have unsynced firewalls at Sites A and B?

If so, please provide more details of the topology,

Thanks

Ian

hi

btw i hve the following H/W config @ Customer end,pls suggest will it be able to run BGP accepting only the default route.

Cisco Internetwork Operating System Software

IOS (tm) C1700 Software (C1700-K8SY7-M), Version 12.2(4)T3, RELEASE SOFTWARE (f

c3)

TAC Support: http://www.cisco.com/tac

Copyright (c) 1986-2002 by cisco Systems, Inc.

Compiled Sun 10-Feb-02 02:32 by ccai

Image text-base: 0x800080E0, data-base: 0x80C09924

ROM: System Bootstrap, Version 12.2(1r)XE1, RELEASE SOFTWARE (fc1)

Hutch-Internet uptime is 7 weeks, 2 days, 18 hours, 45 minutes

System returned to ROM by power-on

System image file is "flash:c1700-k8sy7-mz.122-4.T3.bin"

cisco 1751 (MPC860P) processor (revision 0x600) with 24576K/8192K bytes of memor

y.

Processor board ID JAD06220FNZ (1566080684), with hardware revision 0000

M860 processor: part number 5, mask 2

Bridging software.

X.25 software, Version 3.0.0.

Basic Rate ISDN software, Version 1.1.

1 FastEthernet/IEEE 802.3 interface(s)

2 Serial(sync/async) network interface(s)

1 ISDN Basic Rate interface(s)

32K bytes of non-volatile configuration memory.

16384K bytes of processor board System flash (Read/Write)

Configuration register is 0x2102

System flash directory:

File Length Name/status

1 6569396 c1700-k8sy7-mz.122-4.T3.bin

[6569460 bytes used, 10207756 available, 16777216 total]

16384K bytes of processor board System flash (Read/Write)

prem

hi

in addition to the above msg find the network diagram below in the link mentioned.

http://www.geocities.com/sanjaypremkumar/

Hello,

I assume that your PIX at Location B NATs to ISP B's address space, and the PIX at Location A NATs to ISP A's address space. Therefore, sync between the PIX's won't be an issue since the NAT always pulls the traffic back to the originating firewall (symmetric routing).

To get the optimal outgoing AS path, I would run an IBGP mesh between BA BB CA CB and your two ISP routers. The other option is to inject a default at each site, but then Site A will tend to use ISP A and site B ISP B, whereas with the full IBGP mesh, both sites will get the best AS path.

hi ipotts

thks for the inputs ,but hes already running EIGRP between them for his own use for hving load balancing between the interlinks.

how do i point backup route in location A towards Location B thru PIX ??

if i m not goint to run IBGP with them intenally.

i couldnt understand the exact the logic to such an extent with the pix in picture.though the routers BA,BB & CA,CB coming behind the pix and in private ip sceheme how do i go about in this can u threw some light on this ??

thx all for ur time & help

prem

Hello,

Do you want the traffic to be balanced between both ISPs, (i.e. site A sends to ISP A and ISP B) or do you want a failover scenario where site A always uses ISP A, and site B always uses ISP B. If the local ISP goes down, they use the other ISP.

hi

i need the failover scenario here to be implemented with this setup.

prem

Is it definite that you can't use IBGP, even to inject a default route?

If this is correct, since the PIX only supports RIP in passive mode, and EIGRP can't form a neighbor with a router on a different subnet(i.e. EIGRP updates between your external ISP router and your internal CA,CB routers), and without IBGP, the only option I see is to run RIPv2 between the ISP router and the internal CA,CB routers to inject the default. This will require no validate-update-source under router rip, and rip neighbor statements to get unicast RIP. At CA,CB this RIP route can be redistributed into EIGRP, and if the cost of the interlinks is high enough site A should use ISP A unless ISP A goes down. This is abit messy, but without IBGP, I am struggling for other options for a dynamic failover.

hi

thts not definite.to hve a clear idea as u said i can better choose IBGP to run between Internet and CA,CB routers,should i hv to run IBGP with CA,CB and BA,BB though hes running eigrp between them already.

pls clarfy this point,

btw i hv started preparing the config templates already for the routers w/o IBGP between CA,CB and BA,BB.i will post them(for wetting) once i finish them off.

prem

hi

in addition to tht i hve posted(in the link pasted below) the sample ip schemes used by the customer at present.

http://www.geocities.com/sanjaypremkumar/

prem

To get dynamic failover you need to run a routing protocol over the PIXes. The only routing protocols that I know of which can pass information between interfaces on different subnets are IBGP, IGRP or RIPv2. I would recommend IBGP, since it is designed for this type of multihop application, whereas with IGRP and RIP is it more a case of squeezing a routing protocol to fit a need.

Ideally you would create another transit on the external side of the PIXes so that an IBGP default pulls the traffic to this external transit, then full EBGP tables provide the best exit. However, without this external transit, I wouldn't run a full routing table in EBGP but a default in IBGP since a loop could form.

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