[c-nsp] VSS1440 to ASR1002 - MEC issues

Thu May 7 16:41:36 EDT 2009

Thank you for all your comments both on and off list, we've gone for  
four L3 interfaces (two per router) and I've raised this with our  
account manager for progression :-)

regards
Alasdair


On 2 May 2009, at 23:20, Kevin Graham wrote:

>
> Your original concern was redundancy, so I'd personally go with two  
> L3 interfaces per ASR over a static GEC. You may end up with more  
> traffic over the VSL (as I don't believe there's a ECMP enhancement  
> to prefer same-chassis ports as there is for MEC), but you'll avoid  
> having to depend on UDLD, etc to protect against this type if  
> failure mode.
>
> [sent from my mobile]
>
> On May 2, 2009, at 12:01 AM, Alasdair McWilliam  
> <alasdairm at gmail.com> wrote:
>
> Even if ASR only supports GEC, surely my apparent 'one way' traffic  
> symptoms aren't right? I only have one Gigabit Ethernet link in the  
> Port-Channel, between the ASR and the active chassis within the VSS.  
> When the channel-group command is removed from the ASR's GE  
> interface, and the config moved onto the GE interface, it starts to  
> work a treat, despite the VSS still thinking it's an EtherChannel !
>
> Also, the 'switch accept mode virtual' command was run on the active  
> node when the switches were first converted to VSS and rebooted.
>
> Many thanks
> Alasdair
>
>
>
> On 2 May 2009, at 01:43, Daniel de la Rosa (ddelaros) wrote:
>
> That's correct, ASR1000 GEC only support static VLAN LB at the moment
> and not LACP. So this can only work if you are ok on just using GEC  
> with
> VLANs on both sides as Tassos mentioned. Since you are deploying GEC  
> for
> redundancy, this VLAN static LB should be able to give you what you
> need. Also you need to have the VSS on GEC mode on.
>
> HTH
>
>
> -------------
> Daniel de la Rosa
> CCIE # 4622
> Technical Marketing Engineer
> ERBU, Cisco Systems
>
>
>
>
>
> ASR1000 doesn't -yet- support the well-known EtherChannel/LACP. If i
> remember right, RLS5
> will have it.
>
> There is a feature called VLAN Mapping to Gigabit EtherChannel (GEC)
> Member Links, but i
> don't think it would help you much, since you have L3 portchannels on
> both sides.
>
> http://www.cisco.com/en/US/docs/ios/lanswitch/configuration/guide/ 
> lsw_c
> fg_gecvlan.html
>
> --
> Tassos
>
> Alasdair McWilliam wrote on 01/05/2009 18:29:
> Hello,
>
> I'm currently deploying two Cisco 6509-E chassis with VS-Sup720-10GE
> (in
> a VSS 1440 cluster/configuration) with dual ASR 1002 routers to
> provide
> aggregation of multiple upstream links (running multiple BGP and
> EIGRP
> sessions).
>
> I wanted to utilize MEC between each ASR and each 6509 chassis to
> build
> in as much resilience as possible. However this configuration seems
> to
> be playing up and so I thought I'd ask the experts!
>
> Physical Topology:
>
> ASR Gi0/0/0 into 6509 Chassis 1 Module 1 Port 1
> ASR Gi0/1/0 into 6509 Chassis 2 Module 1 Port 1
>
> The ASR is running IOS-XE 2.3.0 (IOS 12.2(33)XNC) AISK9 with dual
> IOS
> processes.
> The VSS chassis are running IOS 12.2(33)SXI1 ISK9 with a 4x 10GE VSL
> (2
> supervisor 10GE interfaces, 2 10GE interfaces on a 6708-10GE line
> card).
> I'm just using CAT6 between the ASR and the 6748-GE-TX line cards in
> the
> VSS boxes.
>
> ASR configuration:
>
> interface Port-Channel1
> ip address x.x.x.5 255.255.255.252
> ip hello-interval eigrp 100 2
> ip hold-time eigrp 100 6
> ip authentication mode eigrp 100 md5
> ip authentication key-chian eigrp 100 vcoresw1-chain
> ip summary-address eigrp 100 0.0.0.0 0.0.0.0 255
> no ip redirects
> no ip unreachables
> no ip proxy-arp
> no shut
> !
>
> interface Gi0/0/0
> channel-group 1
> no shut
>
> interface Gi0/1/0
> channel-group 1
> no shut
>
> Cisco VSS configuration:
>
> int Gi1/1/1
> no switchport
> channel-group 3 mode on
>
> int Gi2/1/1
> no switchport
> channel-group 3 mode on
>
> int Po3
> desc *** MEC to br1-po1 ***
> no ip redirects
> no ip unreachables
> no ip proxy-arp
> ip vrf forwarding edge-vrf
> ip address x.x.x.6 255.255.255.252
> ip hello-interval eigrp 100 2
> ip hold-time eigrp 100 6
> ip authentication mode eigrp 100 md5
> ip authentication key-chain eigrp 100 br1-chain
> no shut
> !
>
>
>
> The problem I am experiencing seems to be one way traffic between
> the
> VSS cluster and the Border Router. Pinging across this /30 subnet
> does
> not work in either direction. EIGRP relationships build when the Po
> interfaces first come online and then immediately time out moments
> later. The VSS cluster then does not see any further EIGRP traffic
> from
> the ASR. However the ASR seems to think it's successfully building
> an
> adjacency to the VSS. However this times out due to 'retry limit
> exceeded' every minute or so, but seems to think it re-establishes
> again.
>
> This problem persists if we drop the PortChannel to just one Gigabit
> Ethernet interface. The second interface can be shut down or
> actually
> removed from the Po config (eg. no channel-group 1).
>
> The really interesting thing is, with one link, if we remove the
> channel-group comand from the one remaining ASR interface, all of a
> sudden the link springs to life. Pings between the ASR Gi0/0/0
> interface
> and the Po3 VSS interface are successful. EIGRP relationship comes
> up
> immediately and is stable, and routes are exchanged as you'd expect.
>
> How does this work? With the ASR thinking it's a non-etherchannel
> interface, but the VSS thinking it IS an EtherChannel (with 1
> member),
> surely it should just fail?
>
> Am I doing something wrong or could this be a bug in either VSS or
> the ASR?
>
> It's not earth shattering, we could just configure 2 EIGRP sessions
> between the VSS and the ASR (4 in total with 2 ASRs) but don't think
> this is as clean an implementation as MEC across fully redundant
> chassis
> and line cards (one of the big selling points of the VSS !!)
>
> Any help would be much appreciated!
>
> Thanks
> Alasdair
>
>
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