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BigIron RX Series Configuration Guide
53-1001810-01
Overview of BGP4
26
•
KEEPALIVE
•
NOTIFICATION
•
ROUTE REFRESH
OPEN message
After a BGP4 router establishes a TCP connection with a neighboring BGP4 router, the routers
exchange OPEN messages. An OPEN message indicates the following:
•
BGP version – Indicates the version of the protocol that is in use on the router. BGP version 4
supports Classless Interdomain Routing (CIDR) and is the version most widely used in the
Internet. Version 4 also is the only version supported on the device.
•
AS number – A two-byte number that identifies the AS to which the BGP4 router belongs.
•
Hold Time – The number of seconds a BGP4 router will wait for an UPDATE or KEEPALIVE
message (described below) from a BGP4 neighbor before assuming that the neighbor is dead.
BGP4 routers exchange UPDATE and KEEPALIVE messages to update route information and
maintain communication. If BGP4 neighbors are using different Hold Times, the lowest Hold
Time is used by the neighbors. If the Hold Time expires, the BGP4 router closes its TCP
connection to the neighbor and clears any information it has learned from the neighbor and
cached.
You can configure the Hold Time to be 0, in which case a BGP4 router will consider its
neighbors to always be up. For directly-attached neighbors, you can configure the device to
immediately close the TCP connection to the neighbor and clear entries learned from an EBGP
neighbor if the interface to that neighbor goes down. This capability is provided by the fast
external fallover feature, which is disabled by default.
•
BGP Identifier – The router ID. The BGP Identifier (router ID) identifies the BGP4 router to other
BGP4 routers. The device use the same router ID for OSPF and BGP4. If you do not set a router
ID, the software uses the IP address on the lowest numbered loopback interface configured on
the router. If the device does not have a loopback interface, the default router ID is the lowest
numbered IP address configured on the device. For more information or to change the router
ID, refer to
“Changing the router ID”
on page 788.
•
Parameter list – An optional list of additional parameters used in peer negotiation with BGP4
neighbors.
UPDATE message
After BGP4 neighbors establish a BGP4 connection over TCP and exchange their BGP4 routing
tables, they do not send periodic routing updates. Instead, a BGP4 neighbor sends an update to its
neighbor when it has a new route to advertise or routes have changed or become unfeasible. An
UPDATE message can contain the following information:
•
Network Layer Reachability Information (NLRI) – The mechanism by which BGP4 supports
Classless Interdomain Routing (CIDR). An NLRI entry consists of an IP prefix that indicates a
network being advertised by the UPDATE message. The prefix consists of an IP network
number and the length of the network portion of the number. For example, an UPDATE
message with the NLRI entry 192.215.129.0/18 indicates a route to IP network
192.215.129.0 with network mask 255.255.192.0. The binary equivalent of this mask is 18
consecutive one bits, thus “18” in the NLRI entry.
Содержание Brocade DCX
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Страница 318: ...246 BigIron RX Series Configuration Guide 53 1001810 01 Deploying a LAG 8 ...
Страница 418: ...346 BigIron RX Series Configuration Guide 53 1001810 01 SuperSpan 12 ...
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Страница 566: ...494 BigIron RX Series Configuration Guide 53 1001810 01 QoS for the oversubscribed 16 x 10GE modules 18 ...
Страница 582: ...510 BigIron RX Series Configuration Guide 53 1001810 01 Viewing Layer 2 ACLs 20 ...
Страница 634: ...562 BigIron RX Series Configuration Guide 53 1001810 01 Troubleshooting ACLs 21 ...
Страница 642: ...570 BigIron RX Series Configuration Guide 53 1001810 01 Trunk formation 22 ...
Страница 746: ...674 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIP filters 24 ...
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Страница 938: ...866 BigIron RX Series Configuration Guide 53 1001810 01 Displaying MBGP information 27 ...
Страница 950: ...878 BigIron RX Series Configuration Guide 53 1001810 01 Using secure copy 28 ...
Страница 988: ...916 BigIron RX Series Configuration Guide 53 1001810 01 Clearing IS IS information 29 ...
Страница 998: ...926 BigIron RX Series Configuration Guide 53 1001810 01 Configuring BFD for the specified protocol 30 ...
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Страница 1054: ...982 BigIron RX Series Configuration Guide 53 1001810 01 Sample 802 1x configurations 33 ...
Страница 1072: ...1000 BigIron RX Series Configuration Guide 53 1001810 01 IP source guard 35 Syntax show ip source guard ethernet port num ...
Страница 1108: ...1036 BigIron RX Series Configuration Guide 53 1001810 01 sFlow 39 ...
Страница 1190: ...1118 BigIron RX Series Configuration Guide 53 1001810 01 Displaying RIPng information 44 ...
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Страница 1310: ...1238 BigIron RX Series Configuration Guide 53 1001810 01 Displaying OSPFv3 information 48 ...
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