Código fonte Wiki de BGP peering with an ISP

Última modificação por Jean Franco em 2024/06/09 22:16
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1 = Overview =
2
3 When you have your own IPv4/IPv6 address space, it's advantageous to announce it via your router to your ISP - especially if you have multiple providers (multi-homing). Even the lowest end EdgeRouters such as the ER-X and ERL can do a full BGP table.
4
5 == The Prefix Lists ==
6
7 The prefix lists are used to control what routes you get from your ISP, as well as the ones you send (announce).
8
9 {{{policy {
10 prefix-list BGP-ISP-From {
11 rule 10 {
12 action permit
13 le 24
14 prefix 0.0.0.0/0
15 }
16 }
17 prefix-list BGP-ISP-To {
18 rule 10 {
19 action permit
20 prefix 192.0.2.0/24
21 }
22 }
23 prefix-list6 BGP-ISPv6-From {
24 rule 10 {
25 action permit
26 le 64
27 prefix 0::/0
28 }
29 }
30 prefix-list6 BGP-ISPv6-To {
31 rule 10 {
32 action permit
33 le 48
34 prefix 2001:DB8::/32
35 }
36 }
37 }}}}
38
39 The -From prefix lists are for routes you receive (imported) from your ISP, while the -To lists are for routes being exported (announced) to your provider. In the case of IPv4, the smallest globally accepted size most if not all providers announce is /24. For IPv6, the smallest globally accepted size is /48.
40
41 'le' means any prefix smaller (ie: 'le 48' won't allow a /64 IPv6 prefix from your ISP's routing table, but it will allow a /32). 'ge' means any prefix greater (ie: 'ge 56' won't allow a /48, but will allow a /56, /64, or even /128).
42
43 In the above examples, 192.0.2.0/24 is your IPv4 netblock, and 2001:DB8::/32 is your IPv6 one. 0.0.0.0/0 and 0::/0 means match all.
44
45 == The Route Maps ==
46
47 While you can just use prefix lists with BGP to control routes imported and exported, route maps give you much more flexibility and control, and can even include AS path matching.
48
49 {{{policy {
50 route-map BGP-ISPv6-From {
51 rule 10 {
52 action permit
53 match {
54 ipv6 {
55 address {
56 prefix-list BGP-ISPv6-From
57 }
58 }
59 }
60 }
61 }
62 route-map BGP-ISPv6-To {
63 rule 10 {
64 action permit
65 match {
66 ipv6 {
67 address {
68 prefix-list BGP-ISPv6-To
69 }
70 }
71 }
72 }
73 }
74 route-map BGP-ISP-From {
75 rule 10 {
76 action permit
77 match {
78 ip {
79 address {
80 prefix-list BGP-ISP-From
81 }
82 }
83 }
84 }
85 }
86 route-map BGP-ISP-To {
87 rule 10 {
88 action permit
89 match {
90 ip {
91 address {
92 prefix-list BGP-ISP-To
93 }
94 }
95 }
96 }
97 }
98 }}}}
99
100 Like the prefix lists, -To and -From are your specific directions in and out (import and export). They're pretty self explanatory and reference the prefix lists used before.
101
102 == BGP Protocol Configuration ==
103
104 {{{protocols {
105 bgp 65501 {
106 address-family {
107 ipv6-unicast {
108 network 2001:DB8::/32 {
109 }
110 }
111 }
112 neighbor 100.64.100.1 {
113 remote-as 65502
114 route-map {
115 export BGP-ISP-To
116 import BGP-ISP-From
117 }
118 soft-reconfiguration {
119 inbound
120 }
121 update-source 100.64.100.2
122 }
123 neighbor fd00::1 {
124 address-family {
125 ipv6-unicast {
126 route-map {
127 export BGP-ISPv6-To
128 import BGP-ISPv6-From
129 }
130 }
131 }
132 remote-as 65502
133 soft-reconfiguration {
134 inbound
135 }
136 update-source fd00::2
137 }
138 network 192.0.2.0/24 {
139 }
140 parameters {
141 router-id 100.64.100.2
142 }
143 redistribute {
144 connected {
145 }
146 kernel {
147 }
148 static {
149 }
150 }
151 }
152 }}}}
153
154 In the above example, our local router has the IPv4 address of 100.64.100.2 and the IPv6 address of fd00::2 with an ASN of 65501. The BGP enabled router on our ISP side is 100.64.100.1 and fd00::1 with an ASN of 65502. We are assuming that our routers are connected over a non-shared link within one hop. If the BGP router is more than one hop away, you need to configure 'ebgp-multihop' with the appropriate amount of hops away your ISP's router is.
155
156 == Showing BGP Information ==
157
158 {{{user@router1:~$ show ip bgp neighbor
159 BGP neighbor is 100.64.100.2, remote AS 65502, local AS 65501, external link
160 BGP version 4, remote router ID 100.64.100.2
161 BGP state = Established, up for 01w0d05h
162 Last read 01w0d05h, hold time is 90, keepalive interval is 30 seconds
163 Neighbor capabilities:
164 Route refresh: advertised and received (old and new)
165 4-Octet ASN Capability: advertised and received
166 Address family IPv4 Unicast: advertised and received
167 Address family IPv4 Multicast: received
168 Received 2838376 messages, 0 notifications, 0 in queue
169 Sent 20788 messages, 0 notifications, 0 in queue
170 Route refresh request: received 0, sent 0
171 Minimum time between advertisement runs is 30 seconds
172 Update source is 100.64.100.1
173 For address family: IPv4 Unicast
174 BGP table version 6603726, neighbor version 6603716
175 Index 2, Offset 0, Mask 0x4
176 Inbound soft reconfiguration allowed
177 Community attribute sent to this neighbor (both)
178 Inbound path policy configured
179 Outbound path policy configured
180 Route map for incoming advertisements is *BGP-ISP-From
181 Route map for outgoing advertisements is *BGP-ISP-To
182 688930 accepted prefixes
183 1 announced prefixes
184
185 Connections established 1; dropped 0
186 External BGP neighbor may be up to 1 hops away.
187 Local host: 100.64.100.2, Local port: 60803
188 Foreign host: 100.64.100.1, Foreign port: 179
189 Nexthop: 100.64.100.1
190 BGP connection: shared network
191
192 BGP neighbor is fd00::1, remote AS 65502, local AS 65501, external link
193 BGP version 4, remote router ID 100.64.100.1
194 BGP state = Established, up for 01w0d05h
195 Last read 01w0d05h, hold time is 180, keepalive interval is 60 seconds
196 Neighbor capabilities:
197 Route refresh: advertised and received (old and new)
198 4-Octet ASN Capability: advertised and received
199 Address family IPv4 Unicast: advertised
200 Address family IPv6 Unicast: advertised and received
201 Received 686685 messages, 0 notifications, 0 in queue
202 Sent 10394 messages, 0 notifications, 0 in queue
203 Route refresh request: received 0, sent 0
204 Minimum time between advertisement runs is 30 seconds
205 Update source is fd00::2
206 For address family: IPv4 Unicast
207 BGP table version 6603726, neighbor version 6603716
208 Index 1, Offset 0, Mask 0x2
209 Inbound soft reconfiguration allowed
210 Community attribute sent to this neighbor (both)
211 0 accepted prefixes
212 0 announced prefixes
213
214 For address family: IPv6 Unicast
215 BGP table version 858622, neighbor version 858620
216 Index 1, Offset 0, Mask 0x2
217 Community attribute sent to this neighbor (both)
218 Inbound path policy configured
219 Outbound path policy configured
220 Route map for incoming advertisements is *BGP-ISPv6-From
221 Route map for outgoing advertisements is *BGP-ISPv6-To
222 49892 accepted prefixes
223 1 announced prefixes
224
225 Connections established 1; dropped 0
226 Local host: fd00::2, Local port: 179
227 Foreign host: fd00::1, Foreign port: 8044
228 Nexthop: 100.64.100.1
229 Nexthop global: fd00::1
230 BGP connection: shared network}}}
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