jmorris@mwunix.mitre.org (John R. Morris) (09/02/90)
Hi; I am fairly new to Unix and Suns and the "Net" so please bear with me. I have a couple questions about subnetting. I have some 4/110s and one 4/280 which were on a class B network. The 4/280 now has two ethernet interfaces and I want to make it a router, isolating all of my machines from the class B network. I can't seem to do it correctly and Sun-support is not very fast/helpful answering questions. So I found out that this net has thousands of sun-gurus... Anyway, -------| |--------- | | | ---------- | rest | | my of ------|sun4/280|---------- little world | | corner B | ---------- | C | | -------| |--------- On the 4/280 (running Sun OS 4.1) can I do the following:? ie0 (rest of world, Class B) inet 128.29.22.1 netmask 255.255.0.0 broadcast 128.29.255.255 ie1 (my little corner, Class C?) inet 128.29.22.7 netmask 255.255.255.0 broadcast 128.29.22.255 If not, why? Should I change the IP address on the class B side to 128.29.23.1 I'm told I should change the netmask to 255.255.255.0 on both sides but I don't know why. Then, what should my routing look like? Why is the following wrong? Routing tables Destination Gateway Flags Refcnt Use Interface 127.0.0.1 127.0.0.1 UH 1 26 lo0 default Outside gateway UG lots lots ie1 129.83.0.0 128.29.22.1 U 0 100 ie1 128.29.22.0 128.29.22.7 U 27 19396 ie0 128.29.0.0 128.29.22.1 U 0 2 ie1 Any response besides comments on my compentency would be very appreciated. Thanks in advance John Morris PS. I'm jmorris@mwunix.mitre.org (if I need to add that).
jms@tardis.tymnet.com (Joe Smith) (10/08/90)
In article <1990Sep4.232423.17162@rice.edu> jmorris@mwunix.mitre.org (John R. Morris) writes: >I have some 4/110s and one 4/280 which were on a class B network. The >4/280 now has two ethernet interfaces and I want to make it a router, >isolating all of my machines from the class B network. I can't seem to do >it correctly and Sun-support is not very fast/helpful answering questions. >-------| |--------- > | ---------- | >rest | | my > of ------|sun4/280|---------- little >world | | corner > B | ---------- | C >-------| |--------- > >On the 4/280 (running Sun OS 4.1) can I do the following:? > ie0 (rest of world, Class B) > inet 128.29.22.1 netmask 255.255.0.0 broadcast 128.29.255.255 > ie1 (my little corner, Class C?) > inet 128.29.22.7 netmask 255.255.255.0 broadcast 128.29.22.255 >If not, why? Should I change the IP address on the class B side to >128.29.23.1 I'm told I should change the netmask to 255.255.255.0 on both >sides but I don't know why. Purpose of netmask: When a packet is destined for an IP address and the local host has multiple IP interfaces, the netmask is used to determine which interface to send the packet to. foreach interface do network1 = destination_address AND interface_netmask network2 = interface_address AND interface_netmask if ( network1 equals network2 ) then send packet though this interface break out of loop endif endfor no match, go consult the routing tables. With ie0 having a netmask of 255.255.0.0, then all addresses in the form of 128.29.*.* will match, and nothing nothing will go out ie1. Simply setting setting ie1's host address to 128.29.23.1 won't help; that address still matches 128.29.*.*. You will have to set the netmask on both interfaces to 255.255.255.0. This will make addresses in the form 128.28.22.* go to ie0, addresses in the form 128.28.23.* go to ie1, and all other addresses will be compared against the routing tables. This last part includes addresses valid on your class B network (such as 128.28.19.*) as well as addresses outside your network (such as 128.83.*.*). The route daemon does its thing automatically when it detects more than one IP interface; you don't have to do anything other than set the network address and netmask up properly. Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C41 | BIX: smithjoe | 12 PDP-10s still running! "POPJ P," San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga speaks for me."
boyter@uunet.uu.net (Maj Brian Boyter) (10/08/90)
jmorris@mwunix.mitre.org (John R. Morris) writes: >I have some 4/110s and one 4/280 which were on a class B network. The >4/280 now has two ethernet interfaces and I want to make it a router, >On the 4/280 (running Sun OS 4.1) can I do the following:? > ie0 (rest of world, Class B) > inet 128.29.22.1 netmask 255.255.0.0 broadcast 128.29.255.255 > ie1 (my little corner, Class C?) > inet 128.29.22.7 netmask 255.255.255.0 broadcast 128.29.22.255 John, I was holding up on answering your query, waiting for someone who is a true guru to come to the rescue... But I haven't seen an answer posted by anyone else... Anyway, here's my idea of what a "normal" Class-B network would look like: | ----------- | gateway | (e.g. gateway to nsfnet) ----------- |128.29.22.1 | backbone _____________________________________________________ | | | |subnet#1 |subnet#2 |subnet#3 | | | | | | |128.29.22.2 |128.29.22.3 |128.29.22.4 -------- -------- -------- |router| |router| |router| -------- -------- -------- |128.29.23.1 |128.29.24.1 |128.29.25.1 | | | | ------ | ------ | ------ |-|host| |-|host| |-|host| | ------ | ------ | ------ | 128.29.23.2 | 128.29.24.2 | 128.29.25.2 | | | I would use a netmask of 255.255.255.0 on both sides of the routers... If the routers are running routed, or some other routing algorithm, then the routers will learn the routes to the other subnets... If not, you can manually install routes to the other subnets using route(8). I would put the these manual routes in the rc.local... For example, if the gateway didn't talk the right routing protocol to the router, you could just put: route add default 128.29.22.1 2 in the rc.local to provide that missing route.... I hope this helps, Brian Maj. Brian A Boyter boyter@fstc-chville.army.mil ||