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Infrastructure Security: Devices and Media • Chapter 6 373

that this ability has not always been a feature of routers and some older routers or
routers using old firmware or operating systems (OSes) may not provide this func-
tion.This is another reason to keep the router’s firmware and OS up-to-date.To
keep routing tables up-to-date between multiple routers on a network, the routers
can communicate changes to the routing tables via routing protocols.These protocols
are designed to let routers send data to each other with the specific purpose of
keeping the routing tables current across all routers.There are several different
routing protocols with each having specific capabilities and packet formats.These
routing protocols are primarily broken up into two types: link-state and distance-
vector.An example of a distance-vector routing protocol is Routing Information
Protocol (RIP), and an example of a distance-vector routing protocol is Open
Shortest Path First (OSPF).
These routing protocols are great for keeping routing tables up-to-date, and
make the administration of routing within a network much easier.They do come
with a downside, however.Attackers can sometimes add their own entries into
routing tables using these protocols, and can effectively take control of a network.
This type of attack is performed by spoofing the address of another router within a
communication to the target router, and putting the new routing information into
the packet.This attack is not easy, as most routers provide some level of password
security within the routing protocols. However, it is important to be aware of this
potential vulnerability and to make sure that the most secure routing protocols are
being used.
A method of avoiding this problem is to use static routes instead of relying on
routing protocols. Static routes are predefined routes that are manually set in the
routing table. Using static routes eliminates the possibility of a routing table being
modified by attacks exploiting routing protocols.

EXAM WARNING

When taking the Security+ exam, make sure that you understand the
difference between firewalls, routers, and switches. You may be asked
questions that make you choose the best device to use in a particular
situation. Knowing which devices should be implemented separately
and which can be combined will help in some situations. For example,
the basic type of firewall technology available in some routers is suffi-
cient for some environments, and should therefore be considered a valid
option rather than requiring a separate device for each purpose.

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