PPPoE over fiber broadband

[msaltunsaray]

Hi guys,

If i have broadband customers via pppoe over fiber, how do i advertise their public IP addresses via iBGP to my RRs across the MPLS network?

I do see customers public IP addresses in routing table with gateway <pppoe> and also see in BGP advertised routes but just don't know how it advertises.

My BGP configuration is just peering with RRs. No network injections.

Thanks in advance

[Hector Gustavo Serrano Gutierrez]

Hi @msaltunsaray,

I'm not sure I understand your question properly.

Could you please provide more details along with some outputs?

Regards.

[msaltunsaray]

Hi @Hector Gustavo Serrano Gutierrez,

I have a router which is connected to customer equipment via 1Gbps fiber.

I have also pppoe with the customer to provide public IP and internet access.

Typical fiber broadband access so far.

On my router, when I check the BGP advertised routes I see the customer public IP. So it is advertising this public IP to my RRs in MPLS.

My BGP configuration on that router is only iBGP peering with two RR in my MPLS network.

it might be silly but my question is how router advertises those customer public IP addresses? Because my BGP configuration is pretty simple, only peering with RRs.

Thanks

[Hector Gustavo Serrano Gutierrez]

How your Router “knows” the customer’s public IP?
Perhaps as Directly Connected in its Routing Table in that customer’s VRF?
Could you please provide ‘show ip route vrf <VRF_NAME> <CUSTOMER_PUBLIC_IP>’ from your Router (the command asumes it is a Cisco IOS based device)?
Your PE router (I assume) probably has that customer’s public IP as directly connected in its customer’s VRF Routing table and this PE Router is redistributing directly connected VRF routes into BGP VPNv4 thus advertising it to your MPLS RR.
Same way if your PE is instead learning that public IP via its static route configuration or dynamic routing from customer’s router. The “public IP” is being advertised to the MPLS RRs by BGP VPNv4.
You can share some relevant outputs and configuration so we can confirm this if you wish.
I hope this helps.
Cheers.

[msaltunsaray]

Hi @Hector Gustavo Serrano Gutierrez 

Unfortunately I cant send any output as this is real network and because of company restrictions .

But I can say that there is no mpls vpn so it is pure bgp and mpls.

thanks

[Hector Gustavo Serrano Gutierrez]

Hi @msaltunsaray,

Difficult to help with no outputs. You basically need to see in BGP from who you are receiving the route and go to that same device and do the same until you find who originates it.

Regards.

[Giuseppe Larosa · Accepted solution]

Hello Msaltunsaray,

if no L3 VPN is involved all these BGP updates are sent and propagated on address family ipv4 unicast.

I see two possible cases:

a)

the prefixes are locally originated on the PE node terminating the PPPoE service.

in

show ip bgp <prefix>

you will see neighbor set to 0.0.0.0 and weight set to 32768.

b) the prefixes related to the public address pool used by PPPoe service are advertised by some other device and learned via RR server

in this case the show ip bgp <prefix> contains two key informations:

Cluster-List attribute: provide info about the RRS that performed route propagation can be equal to RRS BGP router-id or it can be set to a value representing the cluster-id (a dotted decimal notation like 0.0.0.1) if configured on the RRS.

Originator-id: this field is set to the BGP Router-Id of the device that injected the prefix in iBGP domain.

Both these attributes are inserted by the RRS and are needed for safe reflection of BGP advertisements.

The originator-id tells you what device is generating the prefix.

if your BGP Router-ids are routable

(and they should be if you are using MPLS BGP and making iBGP sessions on loopbacks  BGP router-id = OSPF router-id = LDP router-id = loop0 address is the typical setup)

you can easily telnet/SSH to the stated Originator-iD IP address.

Note:

only show ip bgp <prefix> shows all the BGP attributes associated to the NLRI.

You can also perform show ip bgp <host-route> the router will provide you the output for the most specific prefix including the specified host route.

Looking at

show ip bgp | include <prefix>

does not provide all the required information.

Also show ip route <prefix> does not provide all BGP attributes.

Hope to help

Giuseppe