TCPmag.com
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July 18, 2006
Editor: Dan Hong (dhong 101com.com)
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IN THIS ISSUE OF TCPmag.com:
1. Q&A: Configuring Routers with GLBP and a Virtual IP
Address
2. What's New on TCPMag.com
3. Interesting Employment in Texas, Virginia and Georgia
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1. Q&A: Configuring Routers with GLBP and a Virtual IP
Address
Send your toughest Cisco technical questions to editortcpmag.com
with the subject line "Attn: Scott."
-----------------------------
Scott,
I have a question related to your TCPmag.com Q&A from
Jan 4, 2005,
about HSRP and GLBP
(
http://tcpmag.com/qanda/article.asp?EditorialsID=308).
I'm trying to
configure two 2600 routers with GLBP and a virtual IP
address and I
want to load balance between the two routers. Do I just
configure GLBP
as default for both eth0 ints on the routers?
-- Wes
-----------------------------
Wes,
If you don't have any particular desire for one or the
other of your
routers to be the one in charge [i.e., Active Virtual
Gateway (AVG)] of
the group, then you really don't need to do anything beyond
the
defaults. The devices within a particular group will elect
an AVG, and
it goes from there.
GLBP, or Gateway Load Balancing Protocol, is another way to
make
multiple routers share a virtual IP address to be used for a
default
gateway by hosts. This started many years ago with Cisco's
Hot Standby
Router Protocol (HSRP). Well, ok, there was a variant before
that
called IRDP (ICMP Router Discovery Protocol), which allowed
for gateway
discovery by the clients -- but that's a different story.
The industry has a standard very similar to HSRP called VRRP
(Virtual
Router Redundancy Protocol). Both HSRP and VRRP have a
single active
router per group, so it's all or nothing. Both do quite
well in
maintaining overall network efficiency through a virtual
shared IP
address, so that changes in network functionality are
relatively
unknown to the users.
GLBP handles things a little differently. Instead of a
electing a
single active gateway for all traffic, an AVG is elected.
The
responsibility of the AVG is to actually maintain contact
with all
other GLBP gateways as well as be the sole device to respond
to Address
Resolution Protocol (ARP) requests for the gateway's
virtual IP
address. The AVG will respond to ARP requests in a pseudo
round-robin
way, going through all of the other gateways' information.
With this, we end up with multiple active gateways at the
same time.
Each client may receive different MAC address information
for the same
gateway IP address. With multiple active gateways on the
network,
efficiency is not only maintained like other protocols do
but actually
increased! This MAC address assignment is known as an Active
Virtual
Forwarder (AVF).
All three redundancy protocols have methods of
authenticating among
members of a group, as well as things like timers, tracking
mechanisms,
preempt capability and other fun features. But the bare
minimum to
make things work is simply to enable GLBP on an interface!
Everything
else is optional.
R1(config-if)# glbp 1 ip 172.16.1.1
Obviously you fill in whatever information is specific to
your network
there! But that's all that's required!
After enabling this on your network, though, I suggest you
pay
attention to the performance of circuits, routers and such
to determine
whether further tweaking is necessary. GLBP also gives you
the ability
to choose weighting of certain gateways over others to
control the load
balancing.
For more information, check out:
Cisco IOS IP Application Services Configuration Guide,
Release 12.4:
Configuring GLBP:
http://tinyurl.com/pcrgl
Hope that helps!
-- Scott
Scott Morris, quadruple CCIE, JNCIE and all-around
Uber-Geek, can often
be seen traveling around the world consulting and delivering
CCIE
training. He has recently stepped up as VP of Curriculum
Development
for IPexpert and will oversee a new consulting practice. For
more
information on him check out http://www.ipexpert.com.
Send your questions for this column to editortcpmag.com
with the subject line "Attn: Scott."
Miss a Q&A? Go online to http://tcpmag.com/qanda/
To comment on this Q&A, go to:
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st
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2. What's New on TCPmag.com
NEWS: Cisco Updates CCIE Tracks with Beta, Equipment Changes
Cisco Systems announced last week changes to its Cisco
Certified
Internetwork Expert certification tracks for Service
Provider (SP)
and Routing & Switching (R&S).
http://tcpmag.com/news/article.asp?EditorialsID=1070
NEWS: VPN and Security Services Surging
VPN services were a cash cow last year for service
providers,
generating $23 billion in revenue in 2005. Nor has the VPN
services
market peaked.
http://tcpmag.com/news/article.asp?EditorialsID=1071
NEWS: Cisco Continues Its Acquiring Ways
Cisco Systems Inc. earlier this month nabbed Meetinghouse
Data
Communications Inc., a provider of client-side 802.1X
supplicant
software.
http://tcpmag.com/news/article.asp?EditorialsID=1072
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3. Interesting Employment in Texas, Virginia and Georgia
Job postings courtesy of Monster.com.
Citigroup, Cisco Network Engineer
Position Type: Full-time
Location: Irving, Texas
Salary: Not given
Experience: 2 to 5 years
Desired Education: Bachelor's degree, CCNA, CCDP
The Cisco Network Engineer will be responsible for data
network
engineering definition and design; oversee the build,
validation and
production handover functions for end-of-life equipment
remediation,
as well as the following:
* Perform design testing/certification prior to production
implementation.
* Perform installation and configuration of Cisco switches,
routers,
terminal servers, DSU/CSUs and network management tools.
To learn more, visit:
http://jobsearch.monster.com/getjob.asp?JobID=45794258
-----------------------------
Visa USA, Security Operations Center Analyst
Position Type: Full-time
Location: McLean/Arlington, Virginia
Salary: Not given
Experience: 5+ years
Desired Education: Associate's degree, CCNA, GIAC, CISSP,
Network+,
Linux+, Security+, MCSE, SSCP
Responsibilities:
* Works in 24x7 managed security operations center providing
first-
level monitoring, analysis and response to information
security
alerts events.
* Configure and operate intrusion detection systems, filter
and tune
network intrusion detection sensors to eliminate false
alarms.
* Recognize and differentiate between, potential, successful
and
unsuccessful intrusion attempts and compromises through
review and
analysis of relevant event detail and summary information.
* Provide monitoring and levels of service as well as
interpret and
prioritize threats through use of intrusion detection
systems,
firewalls and other boundary protection devices, and any
security
incident management products deployed.
To learn more, visit:
http://jobsearch.monster.com/getjob.asp?JobID=45766070
-----------------------------
Tandberg, Systems Engineer
Position Type: Full-time
Location: Atlanta, Georgia
Salary: Not given
Experience: Not given
Desired Education: Bachelor's degree, CCNA, MCSE
Job summary:
System administration for Tandberg in the Americas.
Specializing in
Windows operating systems and networks, Exchange based
e-mail.
Providing level II support.
To learn more, visit:
http://jobsearch.monster.com/getjob.asp?JobID=45785164
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