[Enterprise SONiC] BGP Step 2.1 Redistribute routes to BGP process (Optional) Follow

Tested model & firmware version:

• Switch model name:
  DCS203 (AS7362-56X)
  DCS204 (AS7726-32X)
  DCS201~202 [AS5835-54X(T)]

• Edgecore SONiC version:
  202006.4
  202012.2 ~ 202012.4
  202111.0 ~ 202111.3

Procedure: Enter Vty shell and BGP ASN

sonic# configure terminal
sonic(config)# router bgp 65101
sonic(config-router)# address-family ipv4 unicast  // Enter address-family ipv4
sonic(config-router-af)# redistribute connected
sonic(config-router-af)# redistribute kernel
sonic(config-router-af)# redistribute static
sonic(config-router)# end

Note: This configuration example says that redistribute connected route, kernel route and static route to BGP process 

Address-family: Multiprotocol extensions enable BGP to carry routing information for multiple network layer protocols. BGP supports an Address Family Identifier (AFI) for IPv4 and IPv6.

sonic(config-router)# address-family
 ipv4  Address Family
 ipv6  Address Family
 l2vpn Address Family

Note: Route redistribution is used to learn from one routing protocol (static, connected route, and OSPF ....) available to a different routing protocol.

sonic(config-router-af)# redistribute 
  babel Babel routing protocol (Babel) [TBD]
  connected   Connected routes (directly attached subnet or host)
  eigrp       Enhanced Interior Gateway Routing Protocol (EIGRP) [TBD]
  isis        Intermediate System to Intermediate System (IS-IS)
  kernel      Kernel routes (not installed via the zebra RIB)
  nhrp        Next Hop Resolution Protocol (NHRP) [TBD] 
  openfabric  OpenFabric Routing Protocol [TBD]
  ospf        Open Shortest Path First (OSPFv2)
  rip         Routing Information Protocol (RIP) [TBD] 
  static      Statically configured routes
  table       Non-main Kernel Routing Table [TBD] 
  vnc         Virtual Network Control (VNC) [TBD] 
  vnc-direct  VNC direct (not via zebra) routes [TBD]

Note:  Currently, SONiC FRRouting supports redistribute connected, isis, kernel, OSPF, and static only.

Note:   Kernel routes and static routes are different, Kernel routes are configured by Linux command, and static routes are configured by FRR.
For example:

FRR:

sonic# configure terminal 
sonic(config)# ip route 0.0.0.0/0 192.168.1.254

sonic# show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric,
> - selected route, * - FIB route

S>* 0.0.0.0/0 [1/0] via 192.168.1.254, Ethernet48, 00:02:19

Linux command:
Caution: this setting will restore to the default after rebooting the switch.

admin@sonic:~$ sudo ip route add 0.0.0.0/0 via 192.168.1.254
admin@sonic:~$ show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP,
O - OSPF, I - IS-IS, B - BGP, E - EIGRP, N - NHRP,
T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP,
F - PBR, f - OpenFabric,
> - selected route, * - FIB route

K>* 0.0.0.0/0 [0/0] via 192.168.1.254, Ethernet48, 00:00:08