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EVN & VRF Questions 2

July 21st, 2017 in ROUTE 300-101 Go to comments

Question 1

Explanation

Route replication allows shared services because routes are replicated between virtual networks and clients who reside in one virtual network can reach prefixes that exist in another virtual network.

Reference: http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/evn/configuration/xe-3s/evn-xe-3s-book/evn-shared-svcs.html

Question 2

Question 3

Explanation

Path isolation can be achieved by using a unique tag for each Virtual Network (VN) -> Answer A is correct.

Instead of adding a new field to carry the VNET tag in a packet, the VLAN ID field in 802.1q is repurposed to carry a VNET tag. The VNET tag uses the same position in the packet as a VLAN ID. On a trunk interface, the packet gets re-encapsulated with a VNET tag. Untagged packets carrying the VLAN ID are not EVN packets and could be transported over the same trunk interfaces -> Answer E is correct.

Reference: http://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/layer-3-vpns-l3vpn/whitepaper_c11-638769.html

Question 4

Explanation

We are trying to ping the 192.168.1.2 in vrf Yellow but the Serial0/0 interfaces of both routers do not belong to this VRF so the ping fails. We need to configure S0/0 interfaces with the “ip vrf forwarding Yellow” (under interface S0/0) in order to put these interfaces into VRF Yellow.

Question 5

Question 6

Question 7

Explanation

In the link http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst4500/12-2/25ew/configuration/guide/conf/vrf.html there is a notice about route-target command: “Note: This command is effective only if BGP is running.” -> C is correct.

Answer A & F are not correct as only route distinguisher (RD) identifies the customer routing table and “allows customers to be assigned overlapping addresses”.

Answer E is not correct as “When BGP is configured, route targets are transmitted as BGP extended communities”

Question 8

Explanation

With VRF-Lite, if you want to send traffic for multiple virtual networks (that is, multiple VRFs) between two routers you need to create a subinterface for each VRF on each router -> VRF-Lite requires subinterfaces. However, with Cisco EVN, you instead create a trunk (called a Virtual Network (VNET) trunk) between the routers. Then, traffic for multiple virtual networks can travel over that single trunk interface, which uses tags to identify the virtual networks to which packets belong.

Note: Both Cisco EVN and VRF-Lite allow a single physical router to run multiple virtual router instances, and both technologies allow routes from one VRF to be selectively leaked to other VRFs. However, a major difference is the way that two physical routers interconnect. With VRF-Lite, a router is configured with multiple subinterfaces, one for each VRF. However, with Cisco EVN, routers interconnect using a VNET trunk, which simplifies configuration.

Reference: CCNP Routing and Switching ROUTE 300-101 Official Cert Guide

All EVNs within a trunk interface share the same IP infrastructure as they are on the same physical interface -> Answer C is correct.

With EVNs, a trunk interface is shared among VRFs so each command configured under this trunk is applied by all EVNs -> Answer E is correct.

Question 9

Question 10

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