Connecting subnet over PPP

Colin Watson sb.mailinglist at
Wed Nov 19 17:08:16 PST 2003

   I am using the userland ppp with pppoe daemon to setup a pppoe server to
authenticate incoming clients. I want to route a /29 subnet (
to a client. Now I authenticate via a radius server, which frames the IP,
Protocol, and route attributes:

Framed-Protocol = PPP
Framed-IP-Address =
Framed-Route = 1

This appears to assign the connection without problem, and the machines on
the clients side of the network, when assigned one of the subnet's IP's have
no issue pinging out to all hosts. However, when a remote PC attempts to
access one of the public IP's - i.e. ping it - this fails. The FreeBSD
Gateway / PPPoE Server shows lots of ARP unable to resolve messages - I
presume this means it cannot find a mac address for the client. I have
checked the routing table - netstat -ran, and an entry is created for the
subnet in question (via the returned radius attributes):

Internet Dest:      Gateway:     Flags:    Refs:  Use:  Netif:  Expire:    UGSc    1        147    tun0    UH        0        256    tun0        00:05:5b:71..   UHLS2 0        0        ste1

A tcpdump of 'ste0' (the PPPoE Daemon Interface) from an IP the clients
subnet pinging out, shows that the replies are occuring:

17:29:28.984831 PPPoE [ses 0x1b] > icmp: echo
17:29:28.984831 PPPoE [ses 0x1b] > icmp: echo reply

However, if this role is reversed, and a remote IP - in this case (on a different /27 (32->63) network) attempts to ping a PC on
the client network:

17:37:45.214386 PPPoE [ses 0x1b] > icmp: echo
17:37:45.221413 PPPoE [ses 0x1b] > icmp: echo
17:37:45.223422 PPPoE [ses 0x1b] > icmp: echo
17:37:45.321455 PPPoE [ses 0x1b] > icmp: echo
17:37:45.623212 PPPoE [ses 0x1b] > icmp: echo

The client uses a D-Link Router which is set to allow all traffic - It is of
course possible this is misconfigured, however I would like to know if this
configuration *should* be working, or if I have made some grevious error
somewhere, which is preventing the traffic reaching the clients network.

Many Thanks

Colin Watson.

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