extended-community "<extended-community-1> <extended-community-2> …"
Where, the syntax of <extended-community-N> is
[rt|soo]:[<2-byte AS num>:<4-byte num> | <4-byte IP Address>:<2-byte num> | <4-byte AS num>L:<2-byte num> | <first two bytes of AS num>.<last two bytes of AS num>:<2-byte num>]
rt: route target extended community type
soo: site of origin extended community type
<2-byte AS number>: This is a 2-byte AS number; the use of private AS-number is not recommended
<4-byte num>: a 4-byte unsigned number
<4-byte IP address>: a valid host IP address; a network address is not accepted; use of private IP address is not recommended; class-D IP addresses are rejected
<4-byte AS num>: This is a 4-byte AS number; the use of private AS-number is not recommended
<first two bytes of AS num>: This is the number represented by the first two bytes of a four-byte AS number. The use of a private AS-number is not recommended.
<last two bytes of AS num>: This is the number represented by the last two bytes of a four-byte AS number. The use of a private AS-number is not recommended