im a dumb f*** OSPF over GRE between links


Senior Member
Jul 27, 2004
ok guys BGP well that was easy its unicast and there is nothing complicated to it ...

rip is a bit tricky as it is multi and unicast UDP ( so to get it to work you must set the tunnel multicast ... simple enough ...

now that ospf bitch yeah it is multicast and uses its own protocol that aint a problem but the dumb bitch dont like having a mismatched MTU so the link never went into full mode ... hope this helps some one else at some stage ...

here is a script for setting up a gre tunnel on a linux box with a private mini subnet that sets the PTP address properly and TTL to avoid other major headaches

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#Configure Tunnel tun0

/sbin/ip link show tun0 &gt; /dev/null 2&gt;&1
if [ $? != 0 ];then
SR=`ping -c 3 |grep "packet loss" |awk '{print $7}'`

if [ "$SR" == "100%" ];then
LOCAL=`ip addr show dev ppp0 |grep inet |head -1 |cut -d/ -f1 |awk '{print $2}'`
REMOTEIP=`dig +short &lt;HOSTNAME&gt; A IN |tail -1`
if [ "$LOCAL" ] && [ "$REMOTEIP" ];then
/sbin/ip tun del tun0
/sbin/ip tunnel add tun0 mode gre remote $REMOTEIP local $LOCAL ttl 255
/sbin/ip addr add peer dev tun0
/sbin/ip link set tun0 up
/sbin/ip link set tun0 multicast on
#Configure Routes For tun0
/sbin/ip route add $REMOTEIP via $LOCAL dev ppp0 table VPN
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