Community discussions

MikroTik App
 
g18c
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 61
Joined: Sat May 26, 2012 11:11 pm

Having ospf loopback and assigned PPP local-address the same

Sun Jun 24, 2018 3:09 am

Dear all, i have OSPF running but need to check if doing this OK.

I have a remote-PPP-server that has a local loopback interface for OSPF with IP 10.255.255.2.

On this server, I have secret with a local IP of 10.255.255.2, and remote IP of 10.255.255.1.

I have another-server that dials in to the above PPP server, it has a loop back of 10.255.255.1.

When it connects to the PPP server successfully, i check the addresses and can see one static address as 10.255.255.1 assigned to the loopback, and another address 10.255.255.1 assigned to the PPP adapter.

The reason i like this is because for each host i can add a OSPF network entry of 10.255.255.0/24 (assuming i have 254 hosts) and it just picks up the network and works.

Or do i want to make unique IPs for each side of the connection in the secrets, i.e. local=10.10.254.2, remote=10.10.254.1? Are there any problems in "reusing" the OSPF loopback address and one showing static and another showing dynamic, will this cause routing protocol to flap?

This is my central node:

Image

And this is from site 2:

Image
 
g18c
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 61
Joined: Sat May 26, 2012 11:11 pm

Re: Having ospf loopback and assigned PPP local-address the same

Sat Jun 30, 2018 7:02 pm

Hi all, anyone able to comment please? Any suggestion from Mikrotik?
 
japres
just joined
Posts: 6
Joined: Tue Jan 16, 2018 5:14 pm

Re: Having ospf loopback and assigned PPP local-address the same

Wed Jul 04, 2018 1:06 pm

Hello,

Hope you're well.

It would defeat the purpose of having a loopback in the first place. Loopback addresses are used on logical interfaces so that if a link went down, you'd still be able to communicate with it. If your PPP link goes down, that address won't be available, but your Loopback would be.

Personally, I'd keep my loopbacks completely separate, set as a /32 and made as the OSPF router-id, this is typically best practice. Then use completely different subnets for your PPP sessions.

Hope this helps.
 
g18c
Frequent Visitor
Frequent Visitor
Topic Author
Posts: 61
Joined: Sat May 26, 2012 11:11 pm

Re: Having ospf loopback and assigned PPP local-address the same

Tue Jul 10, 2018 8:53 am

Thanks Japress, so each {source,dest} IP should be unique? I see when a PPP server is defined you can set the local server address to something common i.e. 172.16.1.1, and assign remote peers DHCP pool. Then i can keep the loop back address seperate and dedicated per node.

Just want to cut down on address administration of the PPP link IPs as opposed to making them static IP unique for each PPP connection (otherwise the central server will have many IPs for each connection).

Any tips appreciated.
 
japres
just joined
Posts: 6
Joined: Tue Jan 16, 2018 5:14 pm

Re: Having ospf loopback and assigned PPP local-address the same

Fri Jul 13, 2018 10:40 am

Sorry about the delay.

Yeah, so you can set a PPP gateway address, it can be private or public depending on how you're routing and use this as your local address in the PPP profile. I'd keep this separate from any other address, let it be unique for each server.
You could use say 10.1.1.1/24 as your PPP Gateway address and then use the rest of the subnet for your PPP sessions to keep things nice and neat.
You could even set a public IP for your PPP Gateway, then use say a private /24 for your sessions and NAT them out of the gateway address. If you're using OSPF, these subnets can be put in their own area per router and summarised for neatness and efficiency. If you're using Radius, you'd create an IP pool per router and allocate it to the customer based on where they connect to.
You can manage your IP's really nicely this way.
10.1.1.0/24 = London customers
10.1.2.0/24 = Birmingham Customers
10.1.3.0/24 = Manchester Customers

Who is online

Users browsing this forum: clambert and 12 guests