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My old Asus router died a few weeks ago, so I thought I'd set up my Debian box to deal with routing my home network. I have a few complications, but I adapted my configuration from a previously working configuration, and I don't see why I am having intermittent problems. But I am having them! Every so often, my SSH connections to the router (and to the Xen virtual machines hosted by the router) just drop. I am unable to use the router's dns server. I can't ping the router. Etc. All of these things work most of the time, but break down intermittently, for a few minutes at a time. (I can provide more details, but I'm not sure what will be helpful)


# The loopback network interface
auto lo
iface lo inet loopback

# Gigabit ethernet, internal network
auto eth0
allow-hotplug eth0
iface eth0 inet manual

# USB ethernet, internet
auto eth1
allow-hotplug eth1
iface eth1 inet dhcp

# Xen Bridge
auto xlan0
iface xlan0 inet static
  bridge_ports eth0

As I understand it, this is sufficient to create the network interfaces, and even do some switching between Xen hosts and my eth0 interface. I installed and configured Shorewall to manage routing between the bridge and my internet-facing interface:


fw    firewall
net   ipv4
lan   ipv4


net     eth1            detect          dhcp,tcpflags,nosmurfs,routefilter,logmartians
lan     xlan0           detect dhcp,tcpflags,nosmurfs,routefilter,logmartians,routeback,bridge


net all DROP info
fw net ACCEPT info
all all REJECT info


DNS(ACCEPT) fw net
DNS(ACCEPT) lan fw
Ping(ACCEPT) lan fw
... and so on, these all work, when the router is accepting traffic at all.



Also, the router is currently "working", and I checked on a problematic client:

arp infrastructure
infrastructure.mydomain ( at 0:23:54:bb:7d:ce on en0 ifscope [ethernet]

I tried it when the router was down, and I (eventually) got the same response. It took about 30 seconds to return, though.

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