A network engineer is configuring RIP as the routing protocol between multiple PEs and CEs. The engineer must avoid advertising the same routes back to their sources. Which action should be performed on the routers to accomplish this task?
A.
Define the site of origin on each interface.
B.
Configure a different route distinguisher for each prefix.
C.
Define VRFs on each device to separate the traffic.
D.
Enable bidirectional forwarding detection on each device.
The Xconnect as a Client of BidirectionalForwarding Detection (BFD) feature provides a trigger for redundant pseudowire switchover based on BFD's fast failure detection capabilities. (eliminate C and D)
The virtual switch instance (VFI) specifies the VPN ID of a VPLS domain, the addresses of other PE devices
in this domain, and the type of tunnel signaling and encapsulation mechanism for each peer (This is where you create the VFI and associated VCs.) So A is correct
A is correct
From RIP guide
Use the site-of-origin command to set an SoO BGP extended community attribute that is used to identify routes that have originated from a site so that the readvertisement of that prefix back to the source site can be prevented.
https://www.cisco.com/c/en/us/td/docs/routers/ncs6000/software/routing/command/reference/b-routing-cr-ncs6k/b-routing-cr-ncs6k_chapter_01000.pdf
BGP SOO is a BGP extended community attribute and stands for BGP Site of Origin. SoO uniquely identifies the site that has originated the route.
SoO is also useful to prevent routing loops and suboptimal routing, especially used to prevent routing loops on dual-homed sites.
SoO can be used even when IGP is used between PE-CE routers and can also be used when BGP is used between PE-CE routers.
SoO value needs to be defined in one of the below Naming Conventions –
A 16-bit autonomous system number, a colon, and a 32-bit number, for example, 45000:3
A 32-bit IP address, a colon, and a 16-bit number, for example, 192.168.10.2:51
BGP SOO Rule of Operation
SOO is applied on updates coming to PE1 from CE router and when these routes are advertised as VPNV4 route to PE router PE2, the PE2 router doesn’t advertise the routes back to the CE router hence avoiding the routing loop.
I would go for A.
Use the site-of-origin command to set an SoO BGP extended community attribute that is used to identify routes that have originated from a site so that the readvertisement of that prefix back to the source site can be prevented. The SoO extended community uniquely identifies the site from which a provider edge (PE) router has learned a route.
router(config)# router rip
router(config-rip) interface GigabitEthernet 0/1/0/0
router(config-rip-if)# site-of-origin 10.0.0.1:20
Answer "A" looks correct.
Although the SoO is set on BGP address family configuration mode not interface mode, but it is applied to the interface based on this reference.
"The configuration of the SoO extended community allows MPLS VPN traffic to be filtered on a per-site basis. The SoO extended community is configured in an inbound BGP route map on the PE router and is applied to the interface."
https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3850/software/release/16-12/configuration_guide/mpls/b_1612_mpls_3850_cg/configuring_eigrp___mpls_vpn_pe_ce_site_of_origin.pdf
Use the site-of-origin command to set an SoO BGP extended community attribute that is used to identify routes that have originated from a site so that the readvertisement of that prefix back to the source site can be prevented. The SoO extended community uniquely identifies the site from which a provider edge (PE) router has learned a route.
Correct Answer is A
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