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1 PerryLorier 1 See also NetworkingBestPractices
2 PerryLorier 2 ----
3 JohnMcPherson 3 !! Use of RFC:1918 addresses for routers
2 PerryLorier 4 This has issues such as:
3 JohnMcPherson 5 <verbatim>
6 [Host A] <-> [Router B] <-> [Router C] <-> [Router D] <-> [Router E] <-> [Host F ]
7 </verbatim>
2 PerryLorier 8
9 Now, Router B has a route to some RFC:1918 space (perhaps Host A is even on RFC:1918 behind [NAT]), Router D is numbered using RFC:1918 space (differently routable than Router B). Now, if the link from Router D and router E has a smaller [MTU] than the rest of the network, and Router B has reverse path filtering on, then A can no longer talk to F. If A traceroutes to F then it misses seeing D as well for the same reason.
10
11 RFC:1918 is evil and should be avoided at all costs, if you must use it, use it only on the edges on networks you control.
3 JohnMcPherson 12
13 !! IP Aliases
14 Network interfaces can be assigned more than one [IP] address.
15
16 Eg, to create aliases for the range 192.168.0.1 - 192.168.0.20:
17
18 ![FreeBSD]:
19 <verbatim>
20 for i in `jot 20 1` ;
21 do
22 ifconfig fxp0 inet 192.168.0.$i alias ;
23 done
24 </verbatim>
25
26 !Linux distros:
27 (old way)%%%
28 <verbatim>
29 for i in `seq 1 20` ;
30 do
31 ifconfig eth0:$i 192.168.0.$i ;
32 done
33 </verbatim>
34
35 (new way)%%%
36 <verbatim>
37 for i in `seq 1 20` ;
38 do
39 ip addr add 192.168.0.$i dev eth0 ;
40 done
41 </verbatim>
42 This also lets you assign a range, eg:
43 <verbatim>
44 ip addr add 192.168.0.0/24 dev eth0
45 </verbatim>
46 However, old tools like route(8) and ifconfig(8) won't show you anything added using this method.
47
48 ----
49 !!!Other
50 This page discusses the difference in tuning networking on various OS's: http://foureleven.org:81/rosetta-stone-performance-tuning.html
1 PerryLorier 51
52 ----
53 CategoryNetworking

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