On 11/6/2010 9:02 PM, Tom Eastep wrote:
>
> VLANs are are virtual ethernet LANs -- the destination of every packet
> send to the VLAN must be specified by a unique layer 2 (MAC) address
> (exceptions are broadcast and multicast).
>
I'm having an issue with pptpd (Poptop) server on the firewall/router.  It is 
not responding to arp requests for the ppp0 connection.

interfaces
net     eth0            detect          tcpflags,nosmurfs
corp    eth1.2          detect          dhcp,tcpflags,logmartians
corp    eth1.3          detect          dhcp,tcpflags,logmartians
proc    eth1.4          detect          tcpflags,logmartians
proc    eth1.5          detect          tcpflags,logmartians
vpn     ppp+

rules (didn't use tunnels) $PPTPIP is a list of clients defined in params
# Replaces entry in tunnels with ACL
ACCEPT          net:$PPTPIP     $FW             tcp     1723
ACCEPT          $FW             net             47
ACCEPT          net:$PPTPIP     $FW             47

pptpd.conf
localip 10.1.19.1
remoteip 10.1.19.248-253

options.pptpd
proxyarp

Client can connect, can ping router ip, can ping ppp0 address, tcpdump shows 
pings leaving the interface but all we see are arp requests from the target 
asking for the mac.

ping from remote system (vpn client) to host on vlan 4  (ppp0 - 10.1.19.248, 
eth1.4 - 10.1.19.1)

# tcpdump -ni eth1.4 host 10.1.19.248
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1.4, link-type EN10MB (Ethernet), capture size 96 bytes
16:51:05.602191 IP 10.1.19.248 > 10.1.19.4: ICMP echo request, id 1280, seq 
256, 
length 40
16:51:05.602337 arp who-has 10.1.19.248 tell 10.1.19.4
16:51:10.895146 IP 10.1.19.248 > 10.1.19.4: ICMP echo request, id 1280, seq 
512, 
length 40
16:51:10.895327 arp who-has 10.1.19.248 tell 10.1.19.4

The echo request is leaving the interface but the router is making no attempt 
to 
reply to the who-has requests.
tcpdump of the arp traffic during ping from remote client.

# tcpdump -ni eth1.4 arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1.4, link-type EN10MB (Ethernet), capture size 96 bytes
17:02:48.622219 arp who-has 10.1.19.4 tell 10.1.19.1
17:02:48.622367 arp reply 10.1.19.4 is-at 00:0e:0c:af:86:3b
17:02:48.622536 arp who-has 10.1.19.248 tell 10.1.19.4
17:02:53.871295 arp who-has 10.1.19.248 tell 10.1.19.4
....

arping from another host on the same subnet

# arping -I eth0.4 10.1.19.248
ARPING 10.1.19.248 from 10.1.19.254 eth0.4
Sent 7 probes (7 broadcast(s))
Received 0 response(s)

tcpdump while the arping was happening
[r...@platlnxrtr2 shorewall]# tcpdump -ni eth1.4 host 10.1.19.248
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1.4, link-type EN10MB (Ethernet), capture size 96 bytes
16:53:57.843136 arp who-has 10.1.19.248 (Broadcast) tell 10.1.19.254
16:53:58.844487 arp who-has 10.1.19.248 (Broadcast) tell 10.1.19.254
16:53:59.846334 arp who-has 10.1.19.248 (Broadcast) tell 10.1.19.254
16:54:00.848172 arp who-has 10.1.19.248 (Broadcast) tell 10.1.19.254

arp table on router
# arp -an
? (xxx.xxx.xxx.xxx) at 00:10:18:90:20:DB [ether] on eth0
? (10.1.19.254) at 00:13:46:61:B9:4B [ether] on eth1.4
? (10.1.16.2) at 00:26:B9:8D:8A:F1 [ether] on eth1.2
? (10.1.16.19) at 00:17:31:88:3D:22 [ether] on eth1.2
? (10.1.19.248) at * PERM PUP on eth1.4

from /var/log/messages
pppd[13753]: MPPE 128-bit stateless compression enabled
pppd[13753]: found interface eth1.4 for proxy arp
pppd[13753]: local  IP address 10.1.19.1
pppd[13753]: remote IP address 10.1.19.248

It works just fine with this basic config.
# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
PPP-INPUT  all  --  anywhere             anywhere
RH-Firewall-1-INPUT  all  --  anywhere             anywhere

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination
PPP-INPUT  all  --  anywhere             anywhere
RH-Firewall-1-INPUT  all  --  anywhere             anywhere

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

Chain PPP-INPUT (2 references)
target     prot opt source               destination
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:pptp
ACCEPT     gre  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere

Chain RH-Firewall-1-INPUT (2 references)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     icmp --  anywhere             anywhere            icmp any
ACCEPT     esp  --  anywhere             anywhere
ACCEPT     ah   --  anywhere             anywhere
ACCEPT     udp  --  anywhere             224.0.0.251         udp dpt:mdns
ACCEPT     udp  --  anywhere             anywhere            udp dpt:ipp
ACCEPT     tcp  --  anywhere             anywhere            tcp dpt:ipp
ACCEPT     all  --  anywhere             anywhere            state 
RELATED,ESTABLISHED
ACCEPT     tcp  --  anywhere             anywhere            state NEW tcp 
dpt:ssh
REJECT     all  --  anywhere             anywhere            reject-with 
icmp-host-prohibited

I know - ACCEPT     all  --  anywhere             anywhere - is bad.

# tcpdump -ni eth1.4 arp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth1.4, link-type EN10MB (Ethernet), capture size 96 bytes
17:10:22.656250 arp who-has 10.1.19.4 tell 10.1.19.1
17:10:22.656390 arp reply 10.1.19.4 is-at 00:0e:0c:af:86:3b
17:10:22.656557 arp who-has 10.1.19.248 tell 10.1.19.4
17:10:23.295331 arp reply 10.1.19.248 is-at 00:19:b9:33:2f:18

So it has something to do with the shorewall config

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