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Log from #iptables at freenode 2006-07-30
[23:00]<cydj>oh, thanks ..
[23:00]<rlraxne>like your isp is:
[23:00]<rlraxne>ASN: 8452
[23:00]<rlraxne>ASN Name: TEDATA (TEDATA)
[23:00]<cydj>tedata!! I thought it was NOL
[23:00]<rlraxne>IP address: 196.202.31.61
[23:00]<cydj>u r probably right though
[23:01]<rlraxne>am i looking at wrong ip ?
[23:01]<cydj>nope correct
[23:01]<rlraxne>well anyway... the bgp4 routing on the internet will if you simplify stuff look at the as instead of ips
[23:02]<rlraxne>this means that when my isp gets "this packet will go to 196.202.31.61" it will find out how to reach that ip based on a couple of criterias
[23:02]<rlraxne>after a while it will enter the network which belongs to AS=8452
[23:02]<rlraxne>then internet and bgp4 is done with its part, the packet has arrived to 8452
[23:03]<rlraxne>then your isp who has 8452 will then internally route the packet (most likely using OSPF or IS-IS) to the distrouter where you are connected to
[23:03]<cydj>thanks for all the info!
[23:03]<cydj>how do u know so much routing stuff :)
[23:03]<rlraxne>this dist router (usually the one which you use as def gw) will then transmit the packet down to the access switches and *poff* it arrives to the interface where your dsl connetion is plugged in
[23:04]<rlraxne>too much spare time and that im working with networks etc :P
[23:04]<cydj>:)
[23:05]<rlraxne>so if you simplify we can say that BGP4 which is the routing protocol on internet is the thing which connects AS numbers to ipranges so that a packet can travel between two AS hosts
[23:06]<rlraxne>this way a specific AS (isp that is) can have multiple lines and once a packet arrives to one of their border routers they will send it further to the core routers which will then distribute the packet further to the dist router which is closest etc
[23:06]<rlraxne>usually a distrouter use OSPF or IS-IS and contain information on how to reach one of the core routers
[23:07]<rlraxne>the core routers then have full bgp tables (imported through the border routers) so they know which of the border routers to use when they have to send a packet to ip 196.202.31.61, both as "default router" but also as "backup routes"
[23:08]<cydj>thanks man ..
[23:08]<rlraxne>and then we have each border router which contains a limited bgp table, basically a table which involves next hops so the router knows on which interface it should send the packet further when destip is 196.202.31.61.
[23:09]<rlraxne>of course the functions "border" "core" and "distribution" (short: dist) can be a single box
[23:09]<rlraxne>but usually you have the border routers at the peerings points and core at some core location and dist near the end customers, this way its easier to perform error checks if some part dies
[23:10]<rlraxne>say that a fiber between your peering partner and your single core/border/dist router gets chopped off
[23:10]<rlraxne>if you have only a single box you then dont know if its the fiber or if its the peering partners interface which is broken
[23:11]<rlraxne>but if you have a router at the place where your peeringpartner has its equipment you can then easily ping your border router to see if it response... then you know that at least nothing is broken with the fiber
[23:11]<rlraxne>and you can phone your peering partner and let them take a look at the physical location to see what has happend
[23:12]<cydj>thanks for all the info man!
