Which command allows traffic to load-balance in an MPLS Layer 3 VPN configuration?
Which command allows traffic to load-balance in an MPLS Layer 3 VPN configuration?
In an MPLS Layer 3 VPN configuration, load balancing between multiple paths is enabled by using the command 'maximum-paths ibgp number-of-paths'. This command allows the configuration of the maximum number of paths for iBGP routes, which is pertinent to the MPLS architecture as it utilizes iBGP for communication between PE (Provider Edge) routers. The command 'maximum-paths ibgp 2' clearly specifies this functionality, making it the correct option for allowing traffic to load-balance in such configurations.
C is correct. Remember MPLS Layer 3 VPN is used in an iBGP setup and not eBGP. This rules out B as the correct answer.
MPLS L3VPN is used IGP/EBGP(CE-PE) and IGP+MPLS+MBGP[iBGP](PE-PE). That is why the votes are divided.
Answer is C. https://www.cisco.com/c/en/us/td/docs/dcn/nx-os/nexus9000/102x/configuration/label-switching/b-cisco-nexus-9000-series-nx-os-label-switching-configuration-guide-102x/m-configuring-mpls-layer-3-vpn-load-balancing.pdf Example: MPLS Layer 3 VPN Load Balancing The following example shows how to configure iBGP load balancing: configure terminal feature-set mpls feature mpls l3vpn feature bgp router bgp 1.1 bestpath cost-community ignore address-family ipv6 unicast maximum-paths ibgp 4
https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxeibmp.html#wp1037690 This is how I see this based on the mentioned article. In BGP we can set different options for load sharing, depending on the design. With MPLS, we can configure "maximum-path ibgp" or "maximum-path eibgp", where the feature [ibgp] performs multipath forwarding only in PE-PE ibgp MPLS domain, and the feature [eibgp] can use both PE-PE ibgp and PE-CE ebgp domains for multipath calculations. If "maximum-paths eibgp 2" is not offered then "maximum-paths ibgp" is OK for MPLS (PE-PE) scenarios. = Answer "C"
First of all, the correct answer is: maximum-paths eibgp 2 . But it's not here. You have to choose between A and B. Since the iBGP(M-BGP) is deeper in the MPLS, I choose to C.
P and PE using iBGP, PE and CE using eBGP. I think A B C is also correct. I don't know :)
Def. C. It's in this article from Cisco. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/mpls/configuration/guide/mpls_cg/mp_vpn_multipath.html
Copied from Cisco config guide: Example: MPLS Layer 3 VPN Load Balancing The following example shows how to configure iBGP load balancing: configure terminal feature-set mpls feature mpls l3vpn feature bgp router bgp 1.1 bestpath cost-community ignore address-family ipv6 unicast maximum-paths ibgp 4
The command “maximum-paths [ ibgp ] number-of-paths” configures the maximum number of multipaths allowed - MPLS uses ebgp so C is correct.
option corret is: C https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxeibmp.html The maximum-paths eibgp command used to configure Border Gateway Protocol (BGP) multipath load sharing in an Multiprotocol Label Switching (MPLS) virtual private network (VPN) using eBGP and iBGP routes. This feature is configured under a VPN routing and forwarding instance (VRF) in address family configuration mode. The number of multipaths is configured separately for each VRF. The number of paths that can be configured is determined by the version of Cisco IOS software
This question does not tell which BGP load-balance it wants - whether it's iBGP or eBGP
I could have chosen "B" until I read this "https://www.cisco.com/c/en/us/td/docs/ios/12_2sx/feature/guide/fsxeibmp.html#wp1027265". In Cisco document, it says "A" is the answer.
correct is A ==> eibgp
B is correct
Summmary Steps from the article: Configuring BGP Load Balancing for eBGP and iBGP You can configure a Layer 3 VPN load balancing for an eBGP or iBGP network. Prerequisites Ensure that you are in the correct VDC (or use the switchto vdc command). SUMMARY STEPS 1. configure terminal 2. feature- s et mpls 3. feature mpls l3vpn 4. feature bgp 5. router bgp as-number 6. (Optional) bestpath cost-community ignore 7. address-family { ipv4 | ipv6 } unicast 8. maximum-paths [ibgp] number-of-paths 9. (Optional) show running-config bgp 10. (Optional) copy running-config startup-config
Why aren't they offering this answer? #address-family ipv4 vrf ... #maximum-paths eibgp 2 -if the parameter "ibgp" is optional than answer "B" might be closer https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/mpls/configuration/guide/mpls_cg/mp_vpn_multipath.html #maximum-paths [ ibgp ] "number-of-paths"
B) #maximum-paths 2 is only for PE-CE eBGP connections outside of the MPLS domain.
eBGP and iBGP Multipath Load Sharing Configuration Example This following configuration example configures a router in IPv4 address-family mode to select two BGP routes (eBGP or iBGP) as multipaths: Device router bgp 40000 Deviceaddress-family ipv4 vrf RED Devicemaximum-paths eibgp 2 Deviceend This following configuration example configures a router in IPv6 address-family mode to select two BGP routes (eBGP or iBGP) as multipaths: Device router bgp 40000 Deviceaddress-family ipv6 vrf RED Devicemaximum-paths eibgp 2
Fortunately MPLS L3 VPN is only a "describe" topic and not a "configure"...
C is correct