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Hello EE,<br />
<br />
We have a Cisco 4331 router and we have not changed anything. &nbsp;All of a sudden we received an alert that one of our bonded T1 serial interfaces was down. &nbsp;When I look at sh ip int bri I see Status up Protocol down.<br />
<br />
Is there anything I can do as we have not altered any configuration to see what is wrong.
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Hello EE,

We have a Cisco 4331 router and we have not changed anything.  All of a sudden we received an alert that one of our bonded T1 serial interfaces was down.  When I look at sh ip int bri I see Status up Protocol down.

Is there anything I can do as we have not altered any configuration to see what is wrong.

We have 6 bonded T1s and one of the serial interfaces show status up protocol down

A router is a networking device that forwards data packets between computer networks. Routers perform the "traffic directing" functions on the Internet. The most familiar type of routers are home and small office cable or DSL routers that simply pass data, such as web pages, email, IM, and videos between computers and the Internet. More sophisticated routers, such as enterprise routers, connect large business or ISP networks up to the powerful core routers that forward data at high speed along the optical fiber lines of the Internet backbone. Though routers are typically dedicated hardware devices, use of software-based routers has grown increasingly common.

Routers

Networking software modules are interfaced with a framework implemented on the machine's operating system that implements the networking functionality of the operating system. The best known frameworks are the TCP/IP model and the OSI model. Systems typically do not use a single protocol to handle a transmission. Instead they use a set of cooperating protocols, sometimes called a protocol family or protocol suite.[9] Some of the best known protocol suites include: IPX/SPX, X.25, AX.25, AppleTalk and TCP/IP. Other protocols indirectly related to networking include the hypertext transfer protocol (HTTP) and its related technologies, Dynamic Host Configuration Protocol (DHCP), Domain Name Server (DNS) and other Internet protocols.

Networking Protocols

Networking is the process of connecting computing devices, peripherals and terminals together through a system that uses wiring, cabling or radio waves that enable their users to communicate, share information and interact over distances. Often associated are issues regarding operating systems, hardware and equipment, cloud and virtual networking, protocols, architecture, storage and management.