1.3.6 Packet Tracer - Configure Ssh

[Yogprasad Moneta]

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Older AireOS WLCs rely on SNMP as the main protocol for monitor. Majority of the relevant information like client count, number of joined access points, processor and memory usage can be obtained via SNMP query from the tool that monitors, to the WLC.

With 9800 WLC, the focus has been put on telemetry. Telemetry works in a "push" model where WLC sends out relevant information to the server without the need to be queried. Catalyst 9800 still offers SNMP for legacy purposes. Some information can be exclusive to telemetry and some of the OIDs previously available on AireOS are not yet available on 9800.

From Cisco IOS XE Bengaluru 17.6.1, Ethernet Service Port (Management Interface VRF/GigabitEthernet 0) is supported in Cisco Catalyst 9800 Series Wireless Controller.

Prior to this release the Catalyst 9800 WLC could only be monitored with SNMP via its Wireless Management Interface or via Redundancy Management Interface (in case of a standby WLC in HA cluster on versions 17.5.1 and higher).

SNMPv2c is a community-based version of SNMP and all communication between the devices is in clear text. SNMPv3 is the most secure version which offers message integrity checks, authentication and encryption of the packets. SNMPv1 is extremely outdated, but still exists to provide legacy software compatibility. It is not mentioned in this article.

Log into the web interface of the 9800 WLC. Under Administration > Management > SNMP ensure that SNMP is globally enabled. Under Community Strings all currently configured communities and their permission level are displayed:

Downloaded archive file contains multiple .my text files that can either be imported into any third-party SNMP server or simply opened with a text editor. In order to find the OID of a specific object name, you first need to locate the exact file that contains it.

Snmpwalk is an SNMP application that uses SNMP GETNEXT requests to query a network entity for a tree of information. It is present by default on MacOS and most Linux distributions. For SNMPv2c, the command follows the syntax:

Code snippets are written for Python 3.9 and utilize pysnmp module (pip install pysnmp) to make SNMP queries for memory utilization of Catalyst 9800-CL WLC. These examples use the same SNMPv2 community and SNMPv3 user created in one of the previous chapters. Simply replace the variable values and integrate the code within your own custom scripts.

Prime Infrastructure comes preloaded with all the OIDs and integration with WLC simply consists in the addition of the WLC credentials to Prime. With 9800 WLCs, Prime mostly relies on Telemetry to collect majority of the details from the WLC, while the small portion of the information is obtained through SNMP.

Cisco Unified Communications Manager (CUCM) has a Wireless Endpoint Tracking Feature that allows it to approximately track client location based on the AP that the client is connected to. For this feature to work, the CUCM has to pull information from the WLC via SNMP queries.

In this scenario, only OIDs from IF-MIB are officially supported, which makes it possible only to monitor the state of all the interfaces on the standby WLC. Example output from 9800-CL WLC:

Standby WLC state can also be monitored with the query to the active WLC. Only CISCO-LWAPP-HA-MIB and CISCO-PROCESS-MIB MIBs are officially supported. When active WLC in HA is queried, the first response represents the value of the active WLC, while the second response represents the value of the standby WLC.

Wasm extension configuration updates are disruptive (see Issue #13690). The configuration is immediately applied for existing requests and connections, and is not reverted if the outer xDS is rejected.

Race condition with Envoy aggregate cluster when creating an EnvoyFilter and ServiceEntry for the same service. Istio-injected pods are unable to start up due to istio-proxy crashing with a segfault. See Issue #28620 for more information.

Added holdApplicationUntilProxyStarts field to ProxyConfig,allowing it to be configured at the pod level. Should not be used in conjunction withthe deprecated values.global.proxy.holdApplicationUntilProxyStarts value.(Issue #27696)

Improved Gateway certificates to be read and distributed from Istiod, rather than in the gateway pods.This reduces the permissions required in the gateways, improves performance, and makes certificate readingmore extensible. This change is fully backwards compatible with the old mechanism, and requires no changesto your cluster. If required, it can be disabled by setting the ISTIOD_ENABLE_SDS_SERVER=falseenvironment variable in Istiod.(Pull Request #27744)

Improved TLS configuration on sidecar server side inbound paths to enforce TLSv2 version along with recommended cipher suites.If this is not needed or creates problems with non Envoy clients, it can disabled by setting Istiod env variable PILOT_SIDECAR_ENABLE_INBOUND_TLS_V2 to false.(Pull Request #27500)

Updated The ipBlocks/notIpBlocks fields of an AuthorizationPolicy now strictly refer to the source IP address of the IP packet as it arrives at the sidecar. Prior to this release, if using the Proxy Protocol, then the ipBlocks/notIpBlocks would refer to the IP address determined by the Proxy Protocol. Now the remoteIpBlocks/notRemoteIpBlocks fields must be used to refer to the client IP address from the Proxy Protocol.(reference)(usage)(usage) (Issue #22341)

Added support for migration and concurrent use of regular K8S tokens as well as new K8S tokens with audience. This feature is enabled bydefault, can be disabled by REQUIRE_3P_TOKEN environment variable in Istiod, which will require new tokens with audience. TheTOKEN_AUDIENCES environment variable allows customizing the checked audience, default remains istio-ca.(Pull Request #26482)

Improved sidecar injection to not modify the pod securityPolicy.fsGroup which could conflict with existing settings and secret mounts.This option is enabled automatically on Kubernetes 1.19+ and is not supported on older versions.(Issue #26882)

Deprecated installation flags values.global.meshExpansion.enabled in favor of user-managed config and values.gateways.istio-ingressgateway.meshExpansionPorts in favor of components.ingressGateways[name=istio-ingressgateway].k8s.service.ports(Issue #25933)

Added an experimental OpenShift Kubernetes platform profile to istioctl. To install with the OpenShift profile, use istioctl install --set profile=openshift.(OpenShift Platform Setup)(Install OpenShift using istioctl)

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