Enabling Additional Paths
The add-path feature is disabled by default.
NOTE: Note: In some cases, while receiving 1K same routes from more than 64 iBGP neighbors,
BGP sessions holdtime of 10 seconds may flap. The BGP add-path does not update packets for
advertisement and cannot scale to higher numbers. Either reduce the number of routes added or
increase the holddown timer value.
To allow multiple paths sent to peers, use the following commands.
1. Allow the advertisement of multiple paths for the same address prefix without the new paths
replacing any previous ones.
CONFIG-ROUTER-BGP mode
bgp add-path [send | receive | both] count
The range is from 2 to 64.
2. Allow the specified neighbor/peer group to send/ receive multiple path advertisements.
CONFIG-ROUTER-BGP mode
neighbor add-path
3. Configure the maximum number of parallel routes (multipath support) BGP supports.
CONFIG-ROUTER-BGP mode
max-path number
The range is from 2 to 64.
Configuring IP Community Lists
Within the Dell Networking OS, you have multiple methods of manipulating routing attributes.
One attribute you can manipulate is the COMMUNITY attribute. This attribute is an optional attribute that
is defined for a group of destinations. You can assign a COMMUNITY attribute to BGP routers by using an
IP community list. After you create an IP community list, you can apply routing decisions to all routers
meeting the criteria in the IP community list.
IETF RFC 1997 defines the COMMUNITY attribute and the predefined communities of INTERNET,
NO_EXPORT_SUBCONFED, NO_ADVERTISE, and NO_EXPORT. All BGP routes belong to the INTERNET
community. In the RFC, the other communities are defined as follows:
• All routes with the NO_EXPORT_SUBCONFED (0xFFFFFF03) community attribute are not sent to
CONFED-EBGP or EBGP peers, but are sent to IBGP peers within CONFED-SUB-AS.
• All routes with the NO_ADVERTISE (0xFFFFFF02) community attribute must not be advertised.
• All routes with the NO_EXPORT (0xFFFFFF01) community attribute must not be advertised outside a
BGP boundary, but are sent to CONFED-EBGP and IBGP peers.
The Dell Networking OS also supports BGP Extended Communities as described in RFC 4360 — BGP
Extended Communities Attribute.
To configure an IP community list, use these commands.
1. Create a community list and enter COMMUNITY-LIST mode.
CONFIGURATION mode
Border Gateway Protocol IPv4 (BGPv4) 211