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public IP for PPPoE Clients

Posted: Wed Oct 07, 2009 8:04 pm
by captainproton
I have a PPPoE Server running on ether2 that is giving public IPs to clients connected. (23.45.67.x/26)
The (physical) Gateway-Device is connected to ether1. so is added as gateway and is added as address to ether1.

How can I make the Router "forward" or "route" pakets from The PPPoE clients to the gateway?

Here are the symptoms that I can see:
- Mikrotik Router can ping the gateway and Internet-IPs (so the gateway settings and internet connection must be ok)
- from a PPPoE client PC I can ping but not the gateway.
- from the internet I can ping the gateway and

The forwarding/routing between the gateway and the PPPoE Clients seems to be the problem.
May I need to set some static route?

Re: public IP for PPPoE Clients

Posted: Thu Oct 08, 2009 9:02 am
by captainproton
no suggestions?

When I connect to my gateway with a PC, I can easiely access internet. with any of the public IPs that are available to me.
The Mikrotik can also access internet, but not the clients on the PPPoE Server side.

Re: public IP for PPPoE Clients

Posted: Thu Oct 08, 2009 9:25 am
by captainproton
after searching and searching I found a way to make it work.

activating proxy-arp on both ether interfaces...

Why is that so?

I have another installation where the mikrotik router is both gateway(on DSL MOdem) and PPPoE Server for clients. proxy-arp was not required there...!?

Re: public IP for PPPoE Clients

Posted: Fri Oct 09, 2009 3:56 am
by marioclep
in this case proxy-arp solves this issue (this is because your pppoe server acts as a proxy between the gateway and your public clients), but in most cases you should ask your provider to create a /30 subnet between their router and your pppoe server, and then route the entire range of public address address to that /30.

Did I make myself clear or this explanation is a little bit confusing?

Re: public IP for PPPoE Clients

Posted: Fri Oct 09, 2009 9:24 pm
by XTLMeth
Some people call proxy arp pseudo bridging. When you have packet forwarding turned on with proxy arp it's almost like having a layer2 bridge except it's not a true bridge. When your pppoe server hands out an ip to your client user that user is going to try to find the gateway out to the internet but since the gateway and the client are on different interfaces they can't arp each other to form a conversation. Proxy arp fixes this by taking the arp requests and proxying them to the other interfaces on the router. When the arps are proxied the devices have a path to send packets to each other. It's always a good idea to be careful when using proxy arp as proxy arp is almost promiscious and will proxy any arp requests even arps that aren't in your /26 segment.

Re: public IP for PPPoE Clients

Posted: Sat Oct 10, 2009 9:19 am
by captainproton
thanks for the answers. this proxy thing seemed little suspicious to me...
so I tried something else:

Following this wiki solved the problem. And even though I don't know exactly, but somehow I think that this is a better solution than the proxy-arp.

Re: public IP for PPPoE Clients

Posted: Fri Oct 16, 2009 10:22 pm
by Abdock
i want to do the same, providing public IP to clients connecting. but i have more then one range, like couple of /24's would the same ospf work ? what do i need to modify ?

Re: public IP for PPPoE Clients

Posted: Thu Oct 29, 2009 10:32 am
by captainproton
I dont know. i have not used the osfp before. but it should work as well if you reproduce it for the other ranges.

actually I als have more ranges but I have not yet implemented this.

Re: public IP for PPPoE Clients

Posted: Thu Nov 12, 2009 9:01 pm
by Abdock
I am trying to use, just for single range, i dial in pppoe get an ip, but cannot surf !
any modification u did to the wiki ?