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bgp-contd/README.md

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+BGP, Part II
+============
+
+Bla blah, previous BGP Part I shows two networks, 1 single BGP link.
+
+This tutorial, Part II: multiple networks with multiple connections to each other
+
+![BGP network with redundant paths](/bgp-contd/bgp-redundancy.png)
+
+ - two main locations (HQ office, datacenter)
+ - a branch office
+ - high bandwidth connections between two main locations, low bandwidth to branch office
+ - IPv6-only example this time
+
+## Look around
+
+Lots 'o bird config already in place, which looks like the Part I config, but multiple times for each connection.
+
+ * R2: `birdc6 show route`, `birdc show route all <prefix>`
+ * look at the route to 2001:db8:10::/48 from R2 -> two options, one is chosen and ends up in kernel (with the `*`)
+ * look at the route to 2001:db8::/48 from R12 -> same story, either R10 or R11
+ * each AS decides where it sends the traffic, does not have to be the same connection!
+ * traceroute -n from R2 to R12:
+
+        root@R2:/# traceroute6 -n 2001:db8:10::12
+        traceroute to 2001:db8:10::12 (2001:db8:10::12), 30 hops max, 80 byte packets
+         1  2001:db8:0:1::ff  0.470 ms  0.461 ms  0.463 ms
+         2  2001:db8:0:3::10  0.729 ms  0.727 ms  0.638 ms
+         3  2001:db8:10::12  0.935 ms  0.962 ms  0.868 ms
+
+ * look at the route to 2001:db8:20::/48 from R2 -> only connected to R1, one option, notice next-hop
+ * traceroute -n from R2 to R20
+
+        root@R2:/# traceroute6 -n 2001:db8:20::20
+        traceroute to 2001:db8:20::20 (2001:db8:20::20), 30 hops max, 80 byte packets
+         1  2001:db8:0:1::1  0.384 ms  0.353 ms  0.334 ms
+         2  2001:db8:20::20  0.319 ms  0.345 ms  0.252 ms
+
+## Redundancy
+
+ * 2 connections between `AS65000` and `AS65010`
+ * in order not to interrupt traffic in case of a partial outage or maintenance, traffic can move to the other connection
+ * look at `root@R2:/# mtr -n 2001:db8:10::12`
+ * in my case over `R0`, `R10`
+ * go to `R0`, `birdc6`, `show protocols` and `disable ebgp_r10`
+ * look what happens to the mtr, and look at `/var/log/bird/bird6.log`
+ * now look at R1, does it see a route to AS65010? no? why? fix it.
+
+## Peering
+
+ * simply the fact that two networks have an interconnect and exchange prefixes
+
+## Redundancy for the branch office
+
+ * two connections, disable to R1, whoops, not reachable from AS65000 any more
+ * would be nice to
+
+
+## Transit
+
+ * announcing received routes again to another AS
+ * by default BGP will choose the shortest AS path
+
+## Assignments
+
+## Bonus
+
+ * local preference (> AS path!)
+ * med -> derive from next hop igp? also, potatoes
+
+