350-501 · Question #253
An engineer working for a private service provider with employee id: 3994 37 650 is configuring a Cisco device to redistribute OSPF into BGP. Which task enables the device to filter routes?
The correct answer is C. Configure a route map and reference it with the redistribute command. To filter routes during redistribution from OSPF into BGP on a Cisco device, a route map must be configured and then referenced by the redistribute command. Route maps provide flexible control over which routes are redistributed and how their attributes are modified.
Question
An engineer working for a private service provider with employee id: 3994 37 650 is configuring a Cisco device to redistribute OSPF into BGP. Which task enables the device to filter routes?
Options
- AConfigure a distribute list and associate it to the BGP peer interface
- BConfigure a prefix list and associate it to the BGP peer interface
- CConfigure a route map and reference it with the redistribute command
- DConfigure an access list and reference it with the redistribute command
How the community answered
(40 responses)- A10% (4)
- B5% (2)
- C83% (33)
- D3% (1)
Why each option
To filter routes during redistribution from OSPF into BGP on a Cisco device, a route map must be configured and then referenced by the redistribute command. Route maps provide flexible control over which routes are redistributed and how their attributes are modified.
Distribute lists are used for filtering inbound or outbound updates on an interface for a specific routing protocol, not typically for granular control during redistribution between different protocols.
While prefix lists can be used for matching IP prefixes, they are generally applied within a route map or directly to a BGP neighbor, not directly associated with a BGP peer interface to filter redistribution.
When redistributing routes between routing protocols like OSPF and BGP, a route map is the most versatile and recommended tool for filtering and manipulating route attributes. The redistribute command in the BGP routing process can directly reference a route map to control which OSPF routes are advertised into BGP.
Access lists can match IP addresses or networks, but they lack the ability to modify route attributes or perform more complex filtering logic required for robust redistribution filtering, making route maps a superior choice.
Concept tested: Route redistribution filtering with route maps
Source: https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/15-mt/irs-15-mt-book/irs-redistribute-bgp.html
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