<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: Times New Roman; font-size: 12pt; color: #000000'>Jim,<br><br>I don't know if I'm a "senior" network engineer. I know I'm a darn busy one. Maybe I'm a darn busy doofus? I will say that you walk your talk, though. Even "www.ockers.net" is ping-able. I ... can't honestly say I agree with leaving that on, but I see value in your consistency. :-)<br><br>When I recommend turning it off, BTW, I'm referring mostly to ping-sweeps, not to smurf/POD/DDOS attacks. A ping-sweep of a range is often a moron's first step in "target discovery" and sometimes it's just wiser to avoid the morons.<br><br>David L. Willson<br>Trainer, Engineer, Enthusiast<br>MCT MSCE Network+ A+ Linux+ LPIC-1 NovellCLA UbuntuCP<br>tel://720.333.LANS<br>Freeing people from the tyranny (or whatevery) of Microsofty-ness<br><br>----- "Jim Ockers" <ockers@ockers.net> wrote:
<br>>
David L. Willson wrote:
<blockquote cite="mid:266500.861285195944872.JavaMail.dlwillson@dlwillson-laptop">
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<div style="font-family: Times New Roman; font-size: 12pt; color: rgb(0, 0, 0);">> Nate:
Turning off ping responses ~does~ "add security", just like running ssh
on a non-default port, and not returning specific version numbers for
PHP, and other things of that sort. Not providing more info/access than
needed is part of a good security policy. Turning off ping responses
~might~ be appropriate, depending on the circumstances.<br>>
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Well I have to challenge this because as a senior network engineer who
troubleshoots strange problems that confuse everyone else, I find that
a disproportionate share of incidents that land on my desk have to do
with blocked ICMP. I agree with Nate, in almost every case a sysadmin
who blocks ICMP echo request or reply is a doofus. They may be well
meaning but if they actually do it (or if they aren't careful about it)
then they are a doofus.<br>>
<br>>
Blocking ICMP usually adds nearly nothing in security and serves only
to create a lot of confusion. ICMP is an important part of the IP
protocols and people generally expect it to work, so when it doesn't
people tend to make incorrect assumptions about what's not working.
Also, those pesky insecurity-causing type 3 packets are absolutely
critical to allow through from end to end if there is any chance there
is a network connection somewhere along the line with a smaller MTU
than what the sending system expects. Over the years I have seen
several weird application issues caused by ICMP type 3 blocking, so
much so that based on the symptoms that might be one of the first
things I check when I start troubleshooting.<br>>
<br>>
Sure there used to be the old smurf etc. attacks based on incorrect
ICMP handling, but I don't think there have been widespread issues with
ICMP for years now.<br>>
<blockquote cite="mid:266500.861285195944872.JavaMail.dlwillson@dlwillson-laptop">
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<div style="font-family: Times New Roman; font-size: 12pt; color: rgb(0, 0, 0);">> <br>>
OTOH, once on the same IP subnet, an arp request is rarely (never)
declined, and so might make a better test.<br>>
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I think ARP traffic wouldn't be forwarded through a VPN router, since I
think it is on the ethernet segment only.<br>>
<blockquote cite="mid:266500.861285195944872.JavaMail.dlwillson@dlwillson-laptop">
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<div style="font-family: Times New Roman; font-size: 12pt; color: rgb(0, 0, 0);">> <br>>
Dennis: Are you sure the VPN needs to be up to get to the TS? There are
an increasing number of networks with TS available directly to the
Internet.<br>>
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That might be a good idea and Dennis you could try suggest that to your
sysadmin/IT people.<br>>
<br>>
Jim<br>>
<br>>
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