Re: Bizarre Networking Problem
On Thu, 20 Feb 2003 at 7:20pm Bill Moran wrote: Perhaps some output form 'netstat -rn' and 'ifconfig' might provoke some more useful answers. Well the problem is solved, but I am not happy about the solution as it makes absolutely no sense to me. xl0: flags=8943UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST mtu 1500 options=3rxcsum,txcsum inet 192.246.38.10 netmask 0xff00 broadcast 255.255.255.0 inet 208.23.240.10 netmask 0xff00 broadcast 208.23.240.255 ether 00:04:75:b0:24:12 media: Ethernet autoselect (100baseTX full-duplex) status: active The above was the ifconfig when I had the problem. Notice the broadcast addresses. The commands that brought up the interface at boot are: /sbin/ifconfig xl0 192.246.38.10 netmask 255.255.255.0 /sbin/ifconfig xl0 alias 208.23.240.10 netmask 255.255.255.0 (note that the netmask really is not required as those IP's are from traditional class C, but I like to always be specific so I don't forget one when I'm working in 'A' or 'B' space.) So those commands give two different kinds of broadcast addresses and to my way of thinking, the second one (on the 208...) is correct. But if I alias the interface like so: ifconfig inet 208.23.240.10 netmask 0xff00 broadcast 255.255.255.0 The sluggishness on the 208 net goes away. I don't understand it, but it works. I don't like stuff this, it creeps me out. -- Joseph F. Noonan Rigaku/MSC Inc. [EMAIL PROTECTED] To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Bizarre Networking Problem
- Original Message - From: Joseph Noonan [EMAIL PROTECTED] To: Bill Moran [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Friday, February 21, 2003 6:07 PM Subject: Re: Bizarre Networking Problem The above was the ifconfig when I had the problem. Notice the broadcast addresses. The commands that brought up the interface at boot are: /sbin/ifconfig xl0 192.246.38.10 netmask 255.255.255.0 /sbin/ifconfig xl0 alias 208.23.240.10 netmask 255.255.255.0 Hmm, I thought aliases always needed to have netmask of 255.255.255.255. Has something changed? - Mark To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Bizarre Networking Problem
Joseph Noonan wrote: On Thu, 20 Feb 2003 at 7:20pm Bill Moran wrote: Perhaps some output form 'netstat -rn' and 'ifconfig' might provoke some more useful answers. Well the problem is solved, but I am not happy about the solution as it makes absolutely no sense to me. xl0: flags=8943UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST mtu 1500 options=3rxcsum,txcsum inet 192.246.38.10 netmask 0xff00 broadcast 255.255.255.0 inet 208.23.240.10 netmask 0xff00 broadcast 208.23.240.255 ether 00:04:75:b0:24:12 media: Ethernet autoselect (100baseTX full-duplex) status: active The above was the ifconfig when I had the problem. Notice the broadcast addresses. The commands that brought up the interface at boot are: /sbin/ifconfig xl0 192.246.38.10 netmask 255.255.255.0 /sbin/ifconfig xl0 alias 208.23.240.10 netmask 255.255.255.0 (note that the netmask really is not required as those IP's are from traditional class C, but I like to always be specific so I don't forget one when I'm working in 'A' or 'B' space.) So those commands give two different kinds of broadcast addresses and to my way of thinking, the second one (on the 208...) is correct. But if I alias the interface like so: ifconfig inet 208.23.240.10 netmask 0xff00 broadcast 255.255.255.0 That doesn't look right. The broadcast address should be 208.23.240.255 for that IP and 192.246.38.255 for the other one. Can you try these broadcast addys and see if the problem is fixed there as well? The sluggishness on the 208 net goes away. I don't understand it, but it works. I don't like stuff this, it creeps me out. Can't argue with you. I don't see how what you did would fix anything. However, I'm not surprised that ifconfig doesn't guess the right action all the time. I wouldn't get upset if you have to specify the broadcast addy to be sure it's right. -- Bill Moran Potential Technologies http://www.potentialtech.com To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
RE: Bizarre Networking Problem
Well the problem is solved, but I am not happy about the solution as it makes absolutely no sense to me. xl0: flags=8943UP,BROADCAST,RUNNING,PROMISC,SIMPLEX,MULTICAST mtu 1500 options=3rxcsum,txcsum inet 192.246.38.10 netmask 0xff00 broadcast 255.255.255.0 inet 208.23.240.10 netmask 0xff00 broadcast 208.23.240.255 ether 00:04:75:b0:24:12 media: Ethernet autoselect (100baseTX full-duplex) status: active Your nic is set autosense. While probably not the only culprit, if you can manage your 3com switch, hard set the port and your NIC to 100 full duplex. It may not solve the problem, but its one more variable eliminated. I was running a HP 4000M and all the machines set auto. I did a code upgrade on the switch and all of sudden performance went in the gutter because, for some reason, autosense broke. Once I hard set 100fd on everything, performance was once again stellar. The broadcast for 192.246.38.10 is wrong too. You shouldn't have to run in promiscous mode to solve this... Doing so is going to kill your CPU when traffic gets high. Brent To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Bizarre Networking Problem
On Fri, Feb 21, 2003 at 05:17:17PM +, Mark wrote: From: Joseph Noonan [EMAIL PROTECTED] The above was the ifconfig when I had the problem. Notice the broadcast addresses. The commands that brought up the interface at boot are: /sbin/ifconfig xl0 192.246.38.10 netmask 255.255.255.0 /sbin/ifconfig xl0 alias 208.23.240.10 netmask 255.255.255.0 Hmm, I thought aliases always needed to have netmask of 255.255.255.255. Has something changed? Nope. You only use a netmask of 255.255.255.255 when the alias address is the second or subsequent address from a given network. If the alias address is the first one from a distinct network, it should have the regular netmask. Cheers, Matthew -- Dr Matthew J Seaman MA, D.Phil. 26 The Paddocks Savill Way PGP: http://www.infracaninophile.co.uk/pgpkey Marlow Tel: +44 1628 476614 Bucks., SL7 1TH UK To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Netmasks for aliases (was Re: Bizarre Networking Problem)
On Friday 21 February 2003 19:17, Mark wrote: /sbin/ifconfig xl0 192.246.38.10 netmask 255.255.255.0 /sbin/ifconfig xl0 alias 208.23.240.10 netmask 255.255.255.0 Hmm, I thought aliases always needed to have netmask of 255.255.255.255. Has something changed? - Mark Mark, Aliases on the same subnet should always be 255.255.255.255, this does not apply where they are on different subnets, however. Here is a good example, from the ifconfig output of a mail server I set up at an ISP in a nearby town. They used to use a private range, but have since added a public class C which has been broken up into smaller ranges for routing. The mail server, for legacy reasons, still has to serve people on the old IPs because those are still being used by machines in their office, and reconfiguring every office machine with new server IP addresses (they didn't have internal DNS then) would be wasting time. We didn't want to waste public IPs on beancounters, so we just left their machines as is. The host is also serving on the new IP, and acting as a POP server for several virtual domains, which have aliases. The 10.0.1.0/24 range (their office), and the 196.38.113.0/27 range (used for their server farm + virtual domains) are still the same physical network though. The output from ifconfig follows: %ifconfig dc0: flags=8843UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST mtu 1500 inet 196.38.113.2 netmask 0xffe0 broadcast 196.38.113.31 inet6 fe80::a00:8ff:fe00:800%dc0 prefixlen 64 scopeid 0x1 inet 196.38.113.3 netmask 0x broadcast 196.38.113.3 inet 196.38.113.5 netmask 0x broadcast 196.38.113.5 inet 196.38.113.6 netmask 0x broadcast 196.38.113.6 inet 196.38.113.7 netmask 0x broadcast 196.38.113.7 inet 196.38.113.8 netmask 0x broadcast 196.38.113.8 inet 196.38.113.9 netmask 0x broadcast 196.38.113.9 inet 196.38.113.10 netmask 0x broadcast 196.38.113.10 inet 196.38.113.11 netmask 0x broadcast 196.38.113.11 inet 10.0.1.4 netmask 0xff00 broadcast 10.0.1.255 inet 10.0.1.5 netmask 0x broadcast 10.0.1.5 ether 08:00:08:00:08:00 media: Ethernet autoselect (100baseTX full-duplex) status: active lo0: flags=8049UP,LOOPBACK,RUNNING,MULTICAST mtu 16384 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2 inet 127.0.0.1 netmask 0xff00 Note how 196.38.113.2 (the machine's real address) has a netmask of 0xffe0, or 255.255.255.224, and the other addresses in this range (all of them aliases) have 0x, 255.255.255.255. Then look at 10.0.1.4, which is an alias too. It has a netmask of 0xff00, or 255.255.255.0. Now look at 10.0.1.5, an alias used for serving intranet web content to legacy machines. Again, a netmask of 0x. The reason for this is that 10.0.1.4, even though being an alias, is the first address the machine handles on that subnet. Just as 196.38.113.2 is the first address the machine has on the public subnet. Rule of thumb: First address on a subnet, alias or not, has the proper subnet netmask. Every other address on the subnet following that, has 0x, or 255.255.255.255. Will To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message -- Willie Viljoen Freelance IT Consultant 214 Paul Kruger Avenue, Universitas Bloemfontein 9321 South Africa +27 51 522 15 60 +27 51 522 44 36 (after hours) +27 82 404 03 27 (mobile) [EMAIL PROTECTED] To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Netmasks for aliases (was Re: Bizarre Networking Problem)
- Original Message - From: Willie Viljoen [EMAIL PROTECTED] To: Mark [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Sent: Friday, February 21, 2003 7:24 PM Subject: Netmasks for aliases (was Re: Bizarre Networking Problem) On Friday 21 February 2003 19:17, Mark wrote: /sbin/ifconfig xl0 192.246.38.10 netmask 255.255.255.0 /sbin/ifconfig xl0 alias 208.23.240.10 netmask 255.255.255.0 Hmm, I thought aliases always needed to have netmask of 255.255.255.255. Has something changed? - Mark Mark, Aliases on the same subnet should always be 255.255.255.255, this does not apply where they are on different subnets, however. Here is a good example, from the ifconfig output of a mail server I set up at an ISP in a nearby town. They used to use a private range, but have since added a public class C which has been broken up into smaller ranges for routing. The mail server, for legacy reasons, still has to serve people on the old IPs because those are still being used by machines in their office, and reconfiguring every office machine with new server IP addresses (they didn't have internal DNS then) would be wasting time. We didn't want to waste public IPs on beancounters, so we just left their machines as is. The host is also serving on the new IP, and acting as a POP server for several virtual domains, which have aliases. The 10.0.1.0/24 range (their office), and the 196.38.113.0/27 range (used for their server farm + virtual domains) are still the same physical network though. The output from ifconfig follows: %ifconfig dc0: flags=8843UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST mtu 1500 inet 196.38.113.2 netmask 0xffe0 broadcast 196.38.113.31 inet6 fe80::a00:8ff:fe00:800%dc0 prefixlen 64 scopeid 0x1 inet 196.38.113.3 netmask 0x broadcast 196.38.113.3 inet 196.38.113.5 netmask 0x broadcast 196.38.113.5 inet 196.38.113.6 netmask 0x broadcast 196.38.113.6 inet 196.38.113.7 netmask 0x broadcast 196.38.113.7 inet 196.38.113.8 netmask 0x broadcast 196.38.113.8 inet 196.38.113.9 netmask 0x broadcast 196.38.113.9 inet 196.38.113.10 netmask 0x broadcast 196.38.113.10 inet 196.38.113.11 netmask 0x broadcast 196.38.113.11 inet 10.0.1.4 netmask 0xff00 broadcast 10.0.1.255 inet 10.0.1.5 netmask 0x broadcast 10.0.1.5 ether 08:00:08:00:08:00 media: Ethernet autoselect (100baseTX full-duplex) status: active lo0: flags=8049UP,LOOPBACK,RUNNING,MULTICAST mtu 16384 inet6 ::1 prefixlen 128 inet6 fe80::1%lo0 prefixlen 64 scopeid 0x2 inet 127.0.0.1 netmask 0xff00 Note how 196.38.113.2 (the machine's real address) has a netmask of 0xffe0, or 255.255.255.224, and the other addresses in this range (all of them aliases) have 0x, 255.255.255.255. Then look at 10.0.1.4, which is an alias too. It has a netmask of 0xff00, or 255.255.255.0. Now look at 10.0.1.5, an alias used for serving intranet web content to legacy machines. Again, a netmask of 0x. The reason for this is that 10.0.1.4, even though being an alias, is the first address the machine handles on that subnet. Just as 196.38.113.2 is the first address the machine has on the public subnet. Rule of thumb: First address on a subnet, alias or not, has the proper subnet netmask. Every other address on the subnet following that, has 0x, or 255.255.255.255. Will Thanks for clarifying this, Will. :) That was a very lucid and helpful explanation. - Mark To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
Re: Bizarre Networking Problem
Joseph Noonan wrote: I have a really weird networking issue on my firewall box. The machine in question has an ethernet facing a cisco facing the Internet and an ethernet facing the LAN plugged into a 3com 100Mbit switch. My LAN has all of the servers and most of the workstations sitting in the /24 that I've had for 10 years. Some of the newer workstations are now sitting on a /24 that I got from one of my providers when I filled up the old space. On xl0, the LAN ether, I simply added one of the new /24's to the interface with an ifconfig -alias and thought everything was good. And it was for users that only use the LAN for e-mail and www. But when I added some users that started messing around with 25MB pppts or 100MB .docs, the performance became pathetic, like in the single or low double digit kbps. The very same computer, can download a 100MB file from the 'net over a T1 faster than it can get a 50MB file off of my Samba based BSD file server. If I change the machines IP to one in the old /24 everything is fine again. Now it gets really weird. Today, one of my associates was investigating this problem and doing the experiments that document the above facts on two different machine. He called me and told me what he found. I logged into the firewall and started running tcpdump against the one address and also looking at the firewall logs to make sure I wasn't firewalling my own network. A few minutes later one of the users afflicted by this issue called to thank me for fixing the problem. I said eh? I haven't done anything other than look at the problem and I'm stumped. He says whatever, works great now! My associate confirmed this on another machine. Well, it is true, I *did* do something: I put xl0 into promiscuous mode. But why oh why is that fixing what should not even be a problem to begin with? Any klews cheerfully accepted (including hitting me with a clue-by-4 if I'm missing something obvious). Somewhat of a shot in the dark, but ... Is the routing possibly messed up such that an attempt to connect to the aliased IP is being routed through the machine to the other IP on the same interface? I don't see why this would cause such terrible performance, but it's the best guess I have with the information you provide. Perhaps some output form 'netstat -rn' and 'ifconfig' might provoke some more useful answers. -- Bill Moran Potential Technologies http://www.potentialtech.com To Unsubscribe: send mail to [EMAIL PROTECTED] with unsubscribe freebsd-questions in the body of the message
