Hi All have an issue with a network setup. the issue is this some client machines on my network (10 of +- 150) keep losing their connection to our mail server or any other mail server we set up their accounts on. This is an issue with my network because as soon as they are on dialup or iburst or ADSL elsewhere they don't have this issue. I have a 10.0.0.0/8 network which is my internal net. this net routes traffic through 10.0.2.1 (SNAT) which is connected to my DMZ 172.16.0.0/16. the traffic is then sent out to the world via 172.16.0.1(SNAT) over sentech mywireless. I have isolated the issue to being on the 172.16.0.1 machine since a ISDN leased line in the DMZ works 100%. Has anyone experienced similar issues using a shared NATed mywireless .... most of the mail comes down .... it seems to break when transmissions are over +-600 KB) I was told that changing the MTU for the ppp0 device to 1300 would help but no luck there. Also one strange thing I noticed (though I don't know TCP/IP that well) was the txqueuelength value of 3 for the ppp0 interface here is my kernel: 2.6.9-1.667 (FC3) here is ifconfig: eth0 Link encap:Ethernet HWaddr 00:03:47:71:7B:36 inet addr:172.16.0.1 Bcast:172.16.0.255 Mask:255.255.255.0 inet6 addr: fe80::203:47ff:fe71:7b36/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:27879849 errors:0 dropped:0 overruns:0 frame:0 TX packets:26767743 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:669378689 (638.3 MiB) TX bytes:3461641354 (3.2 GiB) eth1 Link encap:Ethernet HWaddr 00:03:47:71:7B:37 inet addr:10.0.7.2 Bcast:10.255.255.255 Mask:255.0.0.0 inet6 addr: fe80::203:47ff:fe71:7b37/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:27333550 errors:0 dropped:0 overruns:0 frame:0 TX packets:28013971 errors:1 dropped:0 overruns:0 carrier:1 collisions:614337 txqueuelen:1000 RX bytes:3798771770 (3.5 GiB) TX bytes:845067479 (805.9 MiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:13651 errors:0 dropped:0 overruns:0 frame:0 TX packets:13651 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:556916 (543.8 KiB) TX bytes:556916 (543.8 KiB) ppp0 Link encap:Point-to-Point Protocol inet addr:196.35.170.61 P-t-P:66.18.87.50 Mask:255.255.255.255 UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1400 Metric:1 RX packets:7595399 errors:0 dropped:0 overruns:0 frame:0 TX packets:7622079 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:3 RX bytes:1453866192 (1.3 GiB) TX bytes:2513716398 (2.3 GiB) and iptables -L: Chain INPUT (policy ACCEPT) target prot opt source destination ACCEPT all -- anywhere anywhere ACCEPT all -- anywhere anywhere DROP tcp -- anywhere anywhere tcp flags:SYN,RST,ACK/SYN DROP tcp -- anywhere anywhere tcp flags:SYN,RST,ACK/SYN Chain FORWARD (policy ACCEPT) target prot opt source destination TCPMSS tcp -- anywhere anywhere tcp flags:SYN,RST/SYN TCPMSS clamp to PMTU ACCEPT all -- anywhere anywhere state RELATED,ESTABLISHED Chain OUTPUT (policy ACCEPT) target prot opt source destination and mii-tool: eth0: negotiated 100baseTx-FD, link ok eth1: no autonegotiation, 10baseT-HD, link ok eth1 is the ether used to connect to the mywireless ... for routing purposes the ip it has assigned isn't really used ... I am using rp-pppoe I think ... Andrew Gargan Developer Interface Media (PTY) Ltd. Tel: 011 507 3003