101 · Question #581
The BIG-IP device has the following configured routes: Which gateway will be chosen to send the packet to the destination 10.238.10.11?
The correct answer is A. 192.168.10.20. BIG-IP selects a gateway using longest prefix match, choosing the route whose network mask most specifically matches the destination address.
Question
The BIG-IP device has the following configured routes:
Which gateway will be chosen to send the packet to the destination 10.238.10.11?
Exhibit
Options
- A192.168.10.20
- B192.168.10.40
- C192.168.10.30
- D192.168.10.10
How the community answered
(16 responses)- A81% (13)
- B13% (2)
- C6% (1)
Why each option
BIG-IP selects a gateway using longest prefix match, choosing the route whose network mask most specifically matches the destination address.
When the BIG-IP routing table is evaluated for destination 10.238.10.11, the longest prefix match algorithm selects the route with the most specific (longest) subnet mask that encompasses the destination IP. The route pointing to gateway 192.168.10.20 has the longest prefix match for 10.238.10.11 among the configured routes. If no more-specific route exists, the default route or most specific static route wins, and the packet is forwarded to that gateway.
Gateway 192.168.10.40 corresponds to a route with a shorter or less specific prefix that does not match 10.238.10.11 as precisely as the route via 192.168.10.20.
Gateway 192.168.10.30 is associated with a route that does not provide the longest prefix match for the destination 10.238.10.11.
Gateway 192.168.10.10 is associated with a route that is less specific than the route via 192.168.10.20 for the given destination address.
Concept tested: BIG-IP routing table longest prefix match selection
Source: https://techdocs.f5.com/en-us/bigip-14-1-0/big-ip-tmos-routing-administration/routing-administration.html
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