Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Instrukcja Użytkownika Pobierz pdf (Strona 98)

Configuring IP Exterior Gateway Protocols (BGP and EGP)

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308628-15.0 Rev 00

Specifying a Time-to-Live Value

Each IP data packet includes a time-to-live (TTL) value. The TTL value specifies

the maximum number of hops that the packet is allowed to traverse in the network

before an intermediate router discards the packet. The TTL counter prevents

packets from looping endlessly through the network. For instructions on setting

the global IP TTL value, see Configuring IP, ARP, RARP, RIP, and OSPF Services.

By default, BGP implements a TTL value as follows:

• IBGP peers use the TTL value set for global IP.

• BGP enforces the one-hop rule for EBGP peers, that is, the remote peer must

be located on a directly attached network.

If you enable multihop connections for EBGP peers, EBGP peers also use the

TTL value set for global IP (see “Enabling Multihop Connections” on page 3-13).

You can specify a TTL value for a BGP session that overrides the TTL value set

for IP. To specify a TTL value for a BGP peer connection, go to a BGP peer

prompt (for example,

box; ip; /jointfilesconvert/97454/bgp; peer/2.2.2.2/2.2.2.3

) and enter:

ttl

<hops>

hops

is the time-to-live value (expressed as the number of hops from 1 through

255) that BGP inserts in outbound updates sent on this peer session. The default

value is 0 (to use the same TTL value set for global IP).

For example, the following command sequence enables multihop connections for

all EBGP peers, configures a session with a remote peer in AS 5, and causes BGP

to insert a TTL value of 4 in each outbound update sent over the peer connection:

/jointfilesconvert/97454/bgp#

multi-hop enabled

/jointfilesconvert/97454/bgp#

peer local 2.2.2.2 remote 3.3.3.3 as 5

peer/2.2.2.2/3.3.3.3#

ttl 4

peer/2.2.2.2/3.3.3.3#

1 2 ... 93 94 95 96 97 98 99 100 101 102 103 ... 275 276

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Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Instrukcja Użytkownika Strona 98