1AGGREGATE(1) General Commands Manual AGGREGATE(1)
2
6 aggregate - optimise a list of route prefixes to help make nice short
7 filters
8
11 aggregate [-m max-length] [-o max-opt-length] [-p default-length] [-q]
12 [-t] [-v]
13
16 Takes a list of prefixes in conventional format on stdin, and performs
17 two optimisations to attempt to reduce the length of the prefix list.
18 The first optimisation is to remove any supplied prefixes which are
20 superfluous because they are already included in another supplied pre‐
21 fix. For example, 203.97.2.0/24 would be removed if 203.97.0.0/17 was
22 also supplied.
23 The second optimisation identifies adjacent prefixes that can be com‐
25 bined under a single, shorter-length prefix. For example, 203.97.2.0/24
26 and 203.97.3.0/24 can be combined into the single prefix 203.97.2.0/23.
27
30 -m max-length
31 Sets the maximum prefix length for entries read from stdin
32 max_length bits. The default is 32. Prefixes with longer lengths
33 will be discarded prior to processing.
34 -o max-opt-length
36 Sets the maximum prefix length for optimisation to max-opt-
37 length bits. The default is 32. Prefixes with longer lengths
38 will not be subject to optimisation.
39 -p default-length
41 Sets the default prefix length. There is no default; without
42 this option a prefix without a mask length is treated as
43 invalid. Use -p 32 -m 32 -o 32 to aggregate a list of host
44 routes specified as bare addresses, for example.
45 -q Sets quiet mode -- instructs aggregate never to generate warning
47 messages or other output on stderr.
48 -t Silently truncate prefixes that seem to have an inconsistent
50 prefix: e.g. an input prefix 203.97.2.226/24 would be truncated
51 to 203.97.2.0/24. Without this option an input prefix
52 203.97.2.226/24 would not be accepted, and a warning about the
53 inconsistent mask would be generated.
54 -v Sets verbose mode. This changes the output format to display the
56 source line number that the prefix was obtained from, together
57 with a preceding "-" to indicate a route that can be suppressed,
58 or a "+" to indicate a shorter-prefix aggregate that was added
59 by aggregate as an adjacency optimisation. Note that verbose
60 output continues even if -q is selected.
62 Aggregate exits 0 on success, and >0 if an error occurs.
63
65 The following list of prefixes:
66 193.58.204.0/22
68 193.58.208.0/22
69 193.193.160.0/22
70 193.193.168.0/22
71 193.243.164.0/22
72 194.126.128.0/22
73 194.126.132.0/22
74 194.126.134.0/23
75 194.151.128.0/19
76 195.42.240.0/21
77 195.240.0.0/16
78 195.241.0.0/16
79 is optimised as followed by aggregate (output shown using the -v flag):
81 aggregate: maximum prefix length permitted will be 24
83 [ 0] + 193.58.204.0/21
84 [ 1] - 193.58.204.0/22
85 [ 2] - 193.58.208.0/22
86 [ 3] 193.193.160.0/22
87 [ 4] 193.193.168.0/22
88 [ 5] 193.243.164.0/22
89 [ 0] + 194.126.128.0/21
90 [ 6] - 194.126.128.0/22
91 [ 7] - 194.126.132.0/22
92 [ 8] - 194.126.134.0/23
93 [ 9] 194.151.128.0/19
94 [ 10] 195.42.240.0/21
95 [ 0] + 195.240.0.0/15
96 [ 11] - 195.240.0.0/16
97 [ 12] - 195.241.0.0/16
98 Note that 193.58.204.0/22 and 193.58.208.0/22 were combined under the
100 single prefix 193.58.204.0/21, and 194.126.134.0/23 was suppressed
101 because it was included in 194.126.132.0/22. The number in square
102 brackets at the beginning of each line indicates the original line num‐
103 ber, or zero for new prefixes that were introduced by aggregate.
104 The output without the -v flag is as follows:
106 193.58.204.0/21
108 193.193.160.0/22
109 193.193.168.0/22
110 193.243.164.0/22
111 194.126.128.0/21
112 194.151.128.0/19
113 195.42.240.0/21
114 195.240.0.0/15
115
117 aggregate-ios(1)
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120 Aggregate was written by Joe Abley <jabley@mfnx.net>, and has been rea‐
121 sonably well tested. It is suitable for reducing customer prefix fil‐
122 ters for production use without extensive hand-proving of results.
123 Autoconf bits were donated by Michael Shields
125 <michael.shields@mfn.com>. The -t option was suggested by Robin John‐
126 son <robbat2@fermi.orbis-terrarum.net>, and the treatment of leading
127 zeros on octet parsing was changed following comments from Arnold Nip‐
128 per <arnold@nipper.de>.
129 An early version of aggregate would attempt to combine adjacent pre‐
131 fixes regardless of whether the first prefix lay on an appropriate bit
132 boundary or not (pointed out with great restraint by Robert Noland
133 <rnoland@2hip.net>).
134
136 Common unix parsing of IPv4 addresses understands the representation of
137 individual octets in octal or hexadecimal, following a "0" or "0x" pre‐
138 fix, respectively. That convention has been deliberately disabled here,
139 since resources such as the IRR do not follow the convention, and con‐
140 fusion can result.
141 For extremely sensitive applications, judicious use of the -v option
143 together with a pencil and paper is probably advisable.
144Joe Abley 2001 November 2 AGGREGATE(1)