Sure,
N9K-SUP-B
version 9.3(6)
Also tried: 7.0(3)I7(8)
Thanks,
-Drew
-----Original Message-----
From: Tim Stevenson (tstevens) <tstev...@cisco.com>
Sent: Friday, June 4, 2021 4:40 PM
To: Drew Weaver <drew.wea...@thenap.com>; 'cisco-nsp@puck.nether.net'
<cisco-nsp@puck.nether.net>
Subject: RE: Nexus Architecture question
Hi Drew,
Can you specify hardware platform and software version here? I am not seeing
what you're seeing, the config I sent blocks a BGP port scan in nmap, and
prevents BGP peering to anything other than the specified IP. I am testing on
Nexus 9500 with 10.1 NXOS; I suspect you are using some other platform eg n5k
or n7k? I may be able to try it out here depending on what you're using.
Thanks,
Tim
-----Original Message-----
From: Drew Weaver <drew.wea...@thenap.com>
Sent: Thursday, June 3, 2021 12:37 PM
To: Tim Stevenson (tstevens) <tstev...@cisco.com>; 'cisco-nsp@puck.nether.net'
<cisco-nsp@puck.nether.net>
Subject: RE: Nexus Architecture question
Hi Tim,
I replied off-list with additional details but I wanted to reply on list to
answer your specific questions:
I copied the strict policy and then edited it with these classes at the top:
policy-map type control-plane Test6
class custom-copp-system-p-bgp-allow
police cir 19000 pps bc 128 packets conform transmit violate drop
class custom-copp-system-p-bgp-deny
police cir 0 pps bc 1 packets conform transmit violate drop
These are the configured class-maps:
Class-map type control-plane match-any custom-copp-system-p-bgp-allow
match access-group name custom-copp-system-p-acl-bgp-allow
Class-map type control-plane match-any custom-copp-system-p-bgp-deny
match access-group name custom-copp-system-p-acl-bgp-deny
These are the configured ACLs:
IP access list custom-copp-system-p-acl-bgp-allow
3 permit tcp 192.168.1.2/32 gt 1023 any eq bgp
4 permit tcp 192.168.1.2/32 eq bgp any gt 1023
IP access list custom-copp-system-p-acl-bgp-deny
1 permit tcp any any eq bgp
10 permit tcp any gt 1023 any eq bgp
20 permit tcp any eq bgp any gt 1023
control-plane
service-policy input Test6
The primary difference that I notice between the two configurations is that
your allow is set to cos 7 and on mine it is not specified and yours is
policing on bps and mine is policing on pps. (I am pretty certain that
throughout the process I have tried it both ways).
I find it a bit hard to follow that on this platform there is no way to write
"just block everything that matches this class" you still have to give it a
"burst" [which I obviously don't want] I understand that behind the scenes the
control plane is supposed to "do the right thing" but it is just difficult to
understand that from reading it.
With this configuration applied:
1) Any host that NMAPs the device sees 179 open.
2) BGP sessions establish (if configured on the Nexus) for hosts that are not
192.168.1.2/32
Is there any way to find out what class traffic from a specific SRC IP or to a
specific port is getting caught at in a CoPP policy?
I suspect that the TCP/179 traffic is just bypassing these classes altogether
and most likely are getting handled further down in the CoPP policy but I
haven't been able to prove that.
Thanks so much.
-Drew
-----Original Message-----
From: Tim Stevenson (tstevens) <tstev...@cisco.com>
Sent: Wednesday, June 2, 2021 5:31 PM
To: Drew Weaver <drew.wea...@thenap.com>; 'cisco-nsp@puck.nether.net'
<cisco-nsp@puck.nether.net>
Subject: RE: Nexus Architecture question
Hi Drew,
In answer to your question about BGP, the BGP process runs only on the
supervisor engine, it does not run on the linecards or anywhere else. It's a
single process, not a per-interface process or anything like that.
Curious how exactly you are configuring CoPP to filter this? With default CoPP,
I get an "open/tcpwrapped" (green) response on TCP 179; I was able to get a
"filtered" (red) response by adding a CoPP class that matches on BGP and
polices to a CIR of 0. I preceeded that class with a class that matches on a
specific neighborship - that BGP neighborship is successfully established while
nmap still returns as filtered from my host.
ip access-list allow-bgp
10 permit tcp 10.1.1.1/32 gt 1023 10.1.1.2/32 eq bgp
20 permit tcp 10.1.1.2/32 eq bgp 10.1.1.1/32 gt 1023 ip access-list drop-bgp
10 permit tcp any any eq bgp
20 permit tcp any eq bgp any
!
class-map type control-plane match-any allow-bgp
match access-group name allow-bgp
class-map type control-plane match-any drop-bgp
match access-group name drop-bgp
!
policy-map type control-plane test-copp-policy-strict
class allow-bgp
set cos 7
police cir 36000 kbps bc 1280000 bytes conform transmit violate drop
class drop-bgp
police cir 0 bps bc 32000 bytes conform transmit violate drop
Hope that helps,
Tim
-----Original Message-----
From: cisco-nsp <cisco-nsp-boun...@puck.nether.net> On Behalf Of Drew Weaver
Sent: Wednesday, June 2, 2021 6:41 AM
To: 'cisco-nsp@puck.nether.net' <cisco-nsp@puck.nether.net>
Subject: [c-nsp] Nexus Architecture question
Has anyone seen a document from Cisco that shows where various processes
running on various Nexus switches actually run from?
For example on a 9508 the nxapi runs in a Linux VM and in order to secure it
you have to drop into the VM and use iptables.
I am trying to figure out where the BGP process lives (for lack of a better
word). Does it run on the line cards? In the control plane? Both? Does it vary
depending on which model and which line cards?
The reason I am asking is because I've noticed that no matter what I do I
cannot seem to "close" the BGP port by using CoPP.
It always shows up as being open when doing a port scan against the system
using NMAP. I know that the switch should not establish a connection with
random hosts but I really am getting hung up on it being 'scannable'/visible at
all.
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