BGP neighbor configuration

[mosssec]

I have one topology

head office: IP: 10.100.100.2 Service Provider: IP 10.100.100.1 subnet Mask: /30 AS Number is : 10001

Remote site_1: IP: 10.100.100.6 Service Provider: IP 10.100.100.5 subnet Mask: /30 AS Number is : 10002

Remote site_2: IP: 10.100.100.10 Service Provider: IP 10.100.100.9 subnet Mask: /30 AS Number is : 10003

I will have to use Ethernet Ports on all sites of the routers.

I have to use the BGP Routing Protocol.

How should be the configuration for each router to make interconnectivity.

Please i need help if some one can do.

[mike987]

R3- 3.3.3.3 connects to R2 and R4 with neighbor statements.
R2&R3 are connected over 100.10.10.0/30 link.
R3 only advertised its internal network 172.33.33.0.
router bgp 300
no synchronization
bgp log-neighbor-changes
network 172.33.33.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 ebgp-multihop 2
neighbor 2.2.2.2 update-source Loopback0
neighbor 4.4.4.4 remote-as 400
neighbor 4.4.4.4 ebgp-multihop 2


R2 with loopback0 2.2.2.2
router bgp 100
no synchronization
bgp log-neighbor-changes
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 update-source Loopback0
neighbor 3.3.3.3 remote-as 300
neighbor 3.3.3.3 ebgp-multihop 2
neighbor 3.3.3.3 update-source Loopback0
neighbor 100.0.0.1 remote-as 100

with update-source Loopback0 routers using loopback interfaces to connect each other, not real IP address of their interfaces. In this case, ebgp-multihop 2 is needed.

[mosssec]

Please find attached herewith file and tell me the full configuration for each site router.

for Head Office i have private Network 192.168.100.0

for Mussafah Factory i have private Network 192.168.200.0

for Al Ashoush Factory i have private Network 192.168.300.0

Please help me.

Best Regards

[mike987]

I see your issues. I'll help you.

Give me a moment to write up you peering statements.

And I'll give you a template to cover whatever networks you will need access from any of your sites that need to me reachable.

I've done a few of these by now.

[mike987]

Home Office

router bgp 10001
bgp router-id 10.100.100.2
nei 10.100.100.1 remote-as 64517


network 192.168.100.0 mask 255.255.255.0

Factory Mussafah

router bgp 10002
bgp router-id 10.100.100.6
nei 10.100.100.5 remote-as 64517

network 192.168.200 mask 255.255.255.0

Factory Al Ashoush

router bgp 10003
bgp router-id 10.100.100.10
nei 10.100.100.9 remote-as 64517

network 192.168.300.0 mask 255.255.255.0

[mike987]

1. You are directly connected to the service provider and so you will not need update-source lo0 for example.
2. You will not need ebgp-multihop since you are directly connected to your isp.

3. By the looks of it you are being tunneled through an MPLS VPN. No biggie. The provider is likely using OSPF to connect your endpoints.

4. You now might need to worry about a faster convergence:

router bgp 10001
timers bgp 10 30 (beats out 60 and 180) Apply it to each of your routers above. When the ISP and each of your routers negotiate they will agree on the lowest values - yours. This will help you more than likely.


5. Policy application enhancement:

nei x.x.x.x bgp soft-reconfiguration-inbound.

6. If you want to inject a default route from the home office to your satellites:


ip router 0.0.0.0 0.0.0.0 x.x.x.x (wherever you want the default route to go -> towards the Internet for example).

router bgp 10001
network 0.0.0.0

7. On the spokes do you need more than the default router? If not:

ip prefix-list default permit 0.0.0.0/0

router bgp 10002 and router bgp 10003
neig 10.100.100.5 prefix-list default in

or

neig 10.100.100.9 prefix-list default in

I think that works... Off the top of my head.

[mike987]

I'd tend to think that the spokes might use the Home office for a default route to the Internet.

This may not be the case in your example. I gave you some quick scripts to inject the 0.0.0.0 from the Home and for each of the spokes to only accept the 0.0.0.0 from the Home Office.

If you do this the spokes will no longer speak directly. They will use the core as a hub and spoke. This may not be deisred at all. So you may want to use the 0.0.0.0 from Home but you may not want to use the prefix-list for example in this case.

[mike987]

Verification:

1. sh ip bgp summary

We are looking to see if any networks are being received. We get worried if we see ACTIVE for instance.

2. sh ip bgp

We want to see those networks we are advertsing and we want to see the networks advertised by the provider, for example, you should see:

10.100.100.0
10.100.100.4
10.100.100.8

192.168.100.0
192.168.200.0
192.168.300.0

and maybe a 0.0.0.0 if you used my example for the Home Office.


If you used the prefix-list for a default route, then you'd only see:

0.0.0.0 on each of your spokes.


3. To troubleshoot and verify:

sh ip bgp nei 10.100.100.1 advertised-routes -> Shows what you sent to the ISP

sh ip bgp nei 10.100.100.1 received-routes -> Shows what you received from the ISP

[mike987]

FYI -

More than likely your ISP is "NOT" peering with you fom a loopback address. So don't assume this is the case.

[mike987]

I sent you an e-mail. If you need specific help with this please let me know. I've done this a few times already and had to work it out in detail. Also you may enounter issues with IGPs that I did not cover in the above examples or may need to use redistribution.

So if you need more help just let me know. We can work it out.